I don't actually think Michael is a bad guy. The way he treated Amber in the immediate aftermath of Casa Amor was awful, but familiar. You see it a lot in guys, I've seen it in guys I've dated (I'm 23 so similar ages to these generation of guys) and they can never just put their hands up and say they fucked up. Their pride gets in the way and they twist it onto the girl. Not excusing this behaviour, but Michael sort of acted that way, then looked awkward for a few days, then apologised. He did realise what he'd done and sorted it out, so I don't think Amber is being weak by holding out hope for him as such as a lot of young lads wouldn't ever say sorry and admit they fucked up. They'd trash talk you even years later when bought up.
In regards to him and Joanna, it does look like he's not as into her as he was Amber. It could either be a case of the producers editing it that way, so that we all speculate (likely) but it could also be he does realise he had a better thing going with Amber and again, be too proud to admit it. If that's the case, Jordan opening the narrative of it being ok to change his mind along with Amber being honest about her feelings tonight could be the push he needs to man up and go for what he wants. He could end up being far more respected from it.
All the stolen glances we see him make at Amber I'm quite wary of, as these could very well be manipulated by producers and cut together. It's the little things that make me think something is missing with him and Joanna, like how Michael used to say him and Amber were like meerkats at night peering over at everyone in their beds and giggling. A few times I've seen Amber and Michael in their separate beds still having a nosey but Joanna fast asleep with her back to him. There doesn't seem to be that fun element.
God that was an essay. I'm far too invested.