i still don’t think tavros has just been sticking with vriska up to now out of spinelessness or stockholm syndrome or anything like that
when vriska initially offered for him to come along, he refused, but then was shown that he didn’t really have that much of a choice in the matter:
and after that, while outwardly acting sycophantic and admiring towards vriska (because if there’s one thing tavros learned in his life, isn’t it that you don’t want to be on vriska serket’s bad side?), he frequently found ways to criticize her and generally act passive-aggressively towards her
he also contradicted himself about having absorbed her memories as tavrisprite, and the only point of that i can figure out is that he wanted her to see him as weaker and less intelligent than he is?
basically his interactions with her seem to be a pattern of sarcastically or directly pointing out her flaws and then switching to a more subservient persona before she actually gets mad at him. given that vriska made it clear at the start that he couldn’t really leave, he does his best to show contempt for her without riling her enough to make his situation worse.
the ring and his apparent desire to get into the flushed quadrant with her could be seen as an extension of this - keep her happy, maybe get some extra power for himself. after all, he knew she had a thing for him before, so maybe he could try to use that for himself? i think it’s interesting that he became so attached to the ring, to the point that he apparently stopped pursuing her after losing it. he points out that it’s a human symbol used to “cEMENT IN STONE THE ROMANTIC MATRIMONIES,” - something more permanent than troll quadrants and therefore potentially a way to get power over her. given how put off he was when vriska first kissed him in hivebent, the apparent change of heart just seems suspicious.
his decision to finally escape seems to stem from a number of things. one, he figured it was worth the risk because he wasn’t just following vriska around while she searched for treasure (which seemed like it may have actually led to some good) and insulted him - now she’s actually leading hundreds of people to their deaths, which he doesn’t want to be complicit in, as he said in the update. the other thing is that she’s a lot busier now - instead of just having tavros to focus on, she’s surrounded by other people, and her psychic powers are being strained to the point where she needs aranea’s help. she didn’t have the extra capacity to control tavros - if she was able to, she probably would have done so instead of just yelling at him. so his situation had not only become more intolerable, but more escapable, and that’s the moment where he finally makes a break for it.