I'm very sorry for what you're going through. However hard it might be for him inside, there's little acknowledge or understanding of what it's like to the be the one left at home.
In some ways, you might have more to deal with than him.
It's normal to be struggling with your feelings and relationship. Not only because you have to come to terms with his actions and choices- and the consequences of them - but because you also have to learn to live with a level of independence you may not be used to.
I urge you to reach out and seek support from groups and charities that support wives and families left behind. The only others who I think could relate to the practicalities are the wives of military men (although they may not welcome the comparison).
You should know you don't have to stay in the relationship if it's too much, there's no guilt with that. Likewise, taking time to yourself is fine.
His emotional demands on you at this time are selfish, however difficult it is for him right now, and demonstrate a lack of understanding and sympathy - and regret - for what you've been put through. It might come from a place of fear and insecurity, which is to be pitied, but your relationship needs more than that to survive. Im sure its hard for him to see you being successful without him, but you are not selfish or uncaring for looking after your needs.
It might help to write a letter, which you can draft as many times as needed, to set out your perspective and give him time to re read and respond to without a knee jerk reaction.
There are no easy answers and the continuation of your relationship will need a lot from both of you (he must realise this - the emotional sacrifice can not all be on your part).
You are not wrong. I cannot comment on how much of his behaviour is ingrained manipulation because I don't know what he was like before his incarceration. If there were elements of control beforehand then you may wish to rethink your relationship. If its new behaviour, then I think you have more chance of coming back from this.
There will be be adjustments to make when he comes out as well and it won't be easy. You're right to take it one bit at a time.
You can be sympathetic, understanding and care while deciding that the relationship is no longer right for you, that's OK. You can also be angry. It will be hard for him to understand the emotional toll on you, but he will need to come to terms with it at some point.
Just continue to take it a bit at a time and don't be guilt tripped. You're doing brilliantly.