Not op but I can post my thoughts sksk Jo has been manipulative in some moments and while it seemed quite innocent to me at first, it's been piling up. Like bandaging his hand so Ian would pity him, deciding not to tell Ian about TJ apologizing (and then he tells him about it suddenly in chapter 45 and changes the topic as soon as the reaction is not what he expected). There's probably more examples but I would need a reread to catch them. He's been expecting a serious relationship from the very beginning and isn't happy about Ian not treating it as such. Also he's known Ian for how long? And he's been talking like he knows him since nearly the beginning. He's possessive and jealous, not wanting Ian to sleep with other guys and especially not TJ. He prevented Ian and TJ from meeting when they had their fight in season 1 deliberately. In chapter 45 he's sweet talking Ian and making it seem like he has a positive attitude towards TJ when it's an attempt at dissuading Ian from looking for TJ ("Don't dismiss that consideration"), "I'm not as kind as you think I am". Also at first when his thoughts turned possessive he would go "what am I thinking?", he doesn't do that anymore, he readily admits it to himself now. Chapter 35 was a huge red flag for me and probably the moment when I started looking at him with more suspicion. And obviously in 52 he literally SAed Ian who was unconscious and didn't consent to Jo cumming on his face.
I don't kno who to root for
The toxic ex that's changing for the better
Or
The walking greenflag with a mysterious past