@Alcemeg that is so so interesting! Especially to see the graduation of the extreme feelings to the less intense and more neutral every day states. I'd say where my husband is concerned I'm in 'submission' and a cross between acceptance and apprehension is definitely a good way to describe it.
@KatySun and @QuentinBunbury you have both been so thoughtful and insightful in your comments and I really do appreciate the time and efforts you've taken to help me untangle my web of thoughts - I hate to think that it's been triggering or draining for either of you but I totally understand why it would be, after all you've dealt with with your own ex's. But thank you again and I hope you're both ok 
In other words, just because he says he needs something, even if argues persuasively and convincingly, does not mean that you have to provide it. You can say no.
This really helped give me a new perspective actually. I think I do feel like I need to submit (or at least attempt) to everything he needs, because of the guilt and the fact that I should be trying everything I can. I've been feeling like I'm in the wrong for not being able to give any more than I feel that I can or have to give, but your post helped me see that that is not necessarily the case!
@Pashazade great point, and the answer is I don't really know, which perhaps in itself answers the question
he does have a lot of likeable qualities objectively, but I think our main connection now is our shared history and our daughter more than anything else. We don't have the same sense of humour or interests and actually in the past (even before the affair) I've really struggled to think of things to talk to him about when we're out on a date or whatever (especially if he's not reciprocating my chat efforts!). I wouldn't turn to him if I was sad or upset and even if I did I don't think he'd know how to comfort me.
I'm glad you talked to your sister. Her crying is not something you did to her. She was being empathetic with you - can you see it that she is crying about how you've been treated? Because she loves you? Maybe you can keep talking to her
Oh, it was awful
we didn't even get into the details as I think she didn't feel qualified to give advice (she's never been in a relationship) so wasn't very forthcoming with the conversation. I was a bit disappointed actually as I asked if she'd ever noticed his treatment of me and she said that she thought it was just 'his way' 
You don't write "because I'm trying". You write, I want to show that I'm trying.[...] Being blunt (again! Sorry!) are you behaving in this way to keep the option open with him for staying?
Good spot!! I think it links in with the need I mentioned a while ago to be in that 'safe space' with him. In order for me to have any chance of a calm and level environment in which I can finally work out and listen to my feelings, he needs to feel calm and happy. For him to feel calm and happy he needs to feel like I'm making an effort. If he doesn't feel that, then he becomes upset and starts talking about us splitting and there being no hope - but I'm never ready to consider that because I don't feel like I've had a chance to properly process everything in a calm way to reach a considered conclusion. So it's a bit of an unhelpful cycle and we're both feeding into it in an unhealthy way.
Its not supposed to be this hard
Yes
I do wonder sometimes if any relationship is ever this difficult and actually manages to get back through to good times, to make all of this anguish worth it?!