When he's with Tav we don't see that, since he just tags along with them and it actually looks like it's better for him to be single when he remains a spawn. It doesn't matter how much someone else loves you, if you don't feel good with yourself then you will not heal. That special someone only becomes your buffer, but once they're gone you'll relapse.
The lonely Astarion spawn is even harder... And, of course, when playing with the unascended is haunted by a sense of helplessness, not only in a practical sense, but also in an emotional sense. Astarion suspects that Tav might betray him and leave (there's no way to prove otherwise, because it's no longer a matter of "lack of lines"). He's adjusting to Tav. He's really trying to act "like Will", i.e. like a "classic romantic guy", he doesn't dare express himself in a way that is characteristic of himself. I felt guilt talking to him very often. "Helplessness-rage-guilt" are the basic underlying emotions that dominate during the "romantic walk" with Astarion Spawn. Even love becomes too painful and not at all "healthy". Although "officially" unhealthy love is considered to be a relationship with the Ascended.
They also travel together, living the same adventurer's lifestyle, but don't really get to experience the true test of a relationship, which is settling down and seeing how you fare with the mundane and responsibilities together.
Ha, and their life together with AA starts with a renovation at the castle, just like a classic couple should after a wedding.
Maybe he will cure some of his fears, but he will cripple himself in the process. When he has so many physical restrictions it will affect his mind and wellbeing. It's horrible to lose something you loved having. Regret is more painful than failure. Frankly I don't buy the notion that purposefully making yourself weaker makes you safer.
Weakening yourself will make you... weaker. As Captain Hindsight would say. It can only work the other way around in DnD, with a kind DM who is sure to give you a bunch of rewards for altruism and lead you to a good, fairy-tale ending. It's good that the writers don't try to deliberately deceive the player and "promise a fairy tale", the game clearly makes it clear that nothing good is going to happen (compare the entry in the diary about Astarion after refusing the ritual, and the entry about Will's father when he breaks the contract with Mizora - in the second case it's clear that the Duke can still be saved, but in the case of Astarion, it's like a very fat hint about the need for a reload). If the player feels like everything is fine and they feel good about it, then a naively romanticized ending is likely to work.
What if they travel around, end up attacked, the night is almost over and the only place nearby where they can hide is someone's house and they don't want to invite him inside?
My first thought is that Tav should rush in and kill the owners of the house with lightning speed (speed potion, action surge) in order to let Astarion in. I realize this is a rhetorical question, I just want to hint that being "good and kind" while constantly having to protect Astarion the Spawn probably won't work. Ascended, like Astarion with a larvae in his head, walks quietly during the day and does not arouse suspicion (only vampire "experts" can identify him, but most people just see him as a white-skinned elf). We'll have to deal not only with monster hunters, but also with random witnesses. We'll have to get our hands dirty anyway.
This outcome would have worked much better if he wasn't a vampire.
This would be a full-fledged version of the "second path" for Astarion. The Ascended would eventually become much more powerful, but he would have to pay the price, and Astarion-Elf would simply become free and be able to start a new life.
In the spawn path they are just as codependent, if not more.
Indeed, even more so. Astarion has lost everything for Tav, he has nothing but Tav, he is attached to her in some ways even forced. Tav is forced to help him and cannot leave him because, "suddenly he will be lost without her". After the Ascension, Astarion no longer needs anyone, he can get along fine on his own, but he wants to be with Tav. Tav has nothing stopping her from going her own way either, but she wants to be with Astarion forever and voluntarily agrees to be his consort. Dependency vs mutual desire.
As for Tav - they have to accomodate their whole lifestyle around Astarion's disabilities - sleep during the day, which is unhealthy and exhausting after a while, travel avoiding rivers, always have to worry about what time it is, find food sources for Astarion, because constantly being his blood bag is also not sound, etc.
The comparison of the spawn's condition with disability has also occurred to me. Talking about self-acceptance in this way evokes associations, as if a person who lost his sight, for example, instead of an operation for 7000$ was offered to accept and love himself blind, arguing that it would be better for him.
He looks amazing on a throne!
Yes, this is so positive!

Found some cute images of the Ascendant on the throne (and just in the castle) in my collection of Astarion pics too.
And to add to the previous topic of the adorable manipulator:
Well, can't you do anything to get that facial expression to change to this:
His scar is also no longer a reminder of his torture, but of the gift he received and what allowed him to keep Tav by his side. He doesn't burn down the palace, but refurbishes and repurposes it for his own needs, and makes new, positive memories with Tav in there.
It seemed to me that he might now want to show off at the camp in a more revealing outfit with an open back. Astarion has a huge wardrobe (when it was possible to buy nice clothes in Baldur), but in the past I always suggested only closed clothes, I was sure he wouldn't want to show off his scars to others, but now it seems he doesn't think so anymore

Cazador copied everything from Vellioth, while Astarion erases the existence of his former master.
Yes, well said!
That's odd, you should be able to bite him!
Oh, I apologize, I inadvertently used a common expression in my language, which is a play on words and does not translate well into English. "Fangs can't come up on him" is a derivative of "hand can't come up on him", which means literally "I can't do any damage to him". I meant I can't bite him, because sinking my fangs into his neck, hurting his delicate white skin.... There's some psychological barrier between "I'd bite you" and doing the actual act, in my case not overcome

Astarion made some totally non-biting vampire for himself

These dialogues are still not working it seems. I tested it in patch 5, even respecced him to a bard and cleric and he had no romantic lines when using healing spells.
But it's nice to listen, to fantasize

Yes, you can summon several types of familiars.

We really need an option to adopt that kitty!
I love the Astarion and kitties-themed fan art!
Basics are very important. Then there's the whole body-mind-soul dynamic. Astarion is not only suffering from mental but also physical trauma. AA has all the time in the world to heal his mind, once his body is working the way he'd like.
We can think of Maslow's pyramid, which describes human needs and prioritizes them in order of importance:
Steps (from bottom to top):
1. Physiological needs
2. Need for security
3. Need for love/ belonging to something
4. Need for respect
5. Need for knowledge
6. Aesthetic needs
7. Need for self-actualization
The last three levels: "cognition", "aesthetic" and "self-actualization" are generally referred to as the Need for Self-Expression (Need for Personal Growth).
Without the fulfillment of the first two needs, the others lose importance. No one thinks about self-actualization when they are starving or in grave danger. It seems to me that caring for the one you love should include the ability to prioritize. You can't do everything at once, you have to do the main thing and then try to take care of the rest.
I have a Tav like that in mind I might create one day.
And it can be a special experience. Evolving and changing your character, getting away from the usual framework allows you to enjoy the game in a special way.