Maybe we're playing a different game. When you first meet Astarion, he comes at you with a knife, but you easily get out of it. He just wanted answers. If he had truly wanted to kill you, he could have. I thought that was kind of the whole point of having the MC get jumped by him. The MC assumes he's just a noble idiot and winds up with a dagger at the throat.
Later, his threats are all in "good fun". He jokes about killing you with a knife, poison, strangulation, etc., but it's all to spark some companion comradery. You can either take offense to it, or joke around with him to share in his sense of humor. It's not serious threats he's sprouting off at you. How often does Astarion try to kill YOU or make threats to YOU? Other than the initial attack, he's always been subservient and friendly to my MCs; ALL of them.
When it comes to sucking your blood, of course he wants you to let him suck your blood. He's never had any people blood, or so he says, and he's starving for it. If you don't let him, it doesn't make him suddenly more of a jerk and he remains in your group. He submissively accepts your decision, just like he does with all of your other choices. He just submits over and over again, going along with whatever you decide unless you decide to attack him or betray him, and he continues to act all friendly no matter how much he disapproves of your decisions.
I don't know. I think he's one of the most powerful origin characters in the party. Use Stealth and cap enemies with Sneak Attack over and over again. He can Stealth just about anywhere at any time. Many times, I couldn't beat the dang Spider Queen without him hiding in shadows and sniping her. So, to me, he isn't weak, he pretends to be subservient, he pretends to be your friend, but over and over again I see "Astarion Disapproves" whenever I do anything nice or good. Unless you are greedy and murderous, he disapproves. So he's obviously ACTING like a flamboyant, weakling who is a slave and needs rescuing from the bad nasty evil Cazador, when really I think he's just using all that pretense to get closer to the MC to mess him/her over in the end... as long as it benefits him.
Heck! i wouldn't be at all surprised if he WAS still working for Cazador. Maybe the whole reason he was captured by mind flayers to begin with and infected was because he was a plant. We have NO idea what villains have their hands in this pot. Raphael, the Absolute, the Dead Three maybe, Shar, Zariel, Lolth, Jergal... all these have been involved already in the EA. Who else might be?
