I think that it's implied that Tav, who recognized how awful he was and thus broke up with him before he could compel them, knows they can't really see him or he will compel them. These months they just didn't see each other. Maybe Tav even run away from him on purpose.
Once again. He can't compel them at the party. Otherwise all the other companions will kill him for it. He can only be there with already compelled Spawn, because, obviously, he told them not to tell anyone they are with him against their will. Hence, you can ask for freedom, he will deny it at the party, but you can't ask other companions for help, because you are already compelled not to.
And all of this doesn't even matter anyway. He still forces Tav to stay with him in the end, when they want break up. It's canon. Period. It's like to say that a man who killed one person isn't a killer, because he could have killed two, three, four people, etc.
Just because he didn't do it in some cases doesn't erase the fact that he is willing and able to do it.
Then walks up to him in a party where he can follow them like an idiot? Not to mention there's endings where the player *clearly* stays in Baldur's Gate so like what he didn't bother looking around?
And the reason you can't ask companions for help when you're not being compelled by him? I'm not sure why you're saying this like it's fact instead of your headcanon. Like this is a video game it's quite easy for devs to have a dialogue choice say one thing then have the companions clearly react to something else being said with player going "oh shit". This isn't some impossibility. A star wars MMO did it over ten years ago.
I didn't say he wasn't willing to do it. I said there's a circumstance *in which he doesn't* which is literally in game. Now if you want to argue that it shouldn't *be* in game fair enough but it's been there as long as the epilogue has been.