Well, I guess you always assume the worst, since you got the worst, right Aud!? My H used to say I should have a little faith in him ... ha, why should I, since he proved that I can't have any faith in him at all, because of his actions.
I think your H is unrealistic to expect you to trust him, and expect the best so soon after his betrayal. He has to do some work too, and should allow you some leeway. Good grief! You walked in on him and OW! I doubt I could take my H back if he had done that. You are truly a strong, forgiving person, Aud. Your H should be grateful for you, and grovelling at your feet, begging for forgiveness. But, they like to forget what they did, and make the LBS look like they are being paranoid.
As for communication ... that is a hairball for me too. I just don't know how to get through to my H, and as you know, have now given up trying for the time being. It is understandable that you will feel a certain amount of mistrust for awhile, and it's going to be difficult to hide it, and plus, your H may read into your communications to him, what he thinks is there, but maybe it's not. Does that make sense? He may be projecting his own insecurities by saying, "don't always assume the worse."
As for becoming that person with low expectations .... it will come with time, I think. I don't know what actions you can take, that you haven't already taken. You have been so awesome in how you have dealt with your sitch, that there is very little you can do differently, I think. It really is up to your H now, I think, to allay your fears and to live his life transparently, so that you can build up your trust.
As I always say, "Piecing sucks!"
I like Phoenix's analogy about the canoe.
Me:57 H:52 M:28 Got another lawyer last year and filed. D35,S/D twins28,D22 EA4/04 End? Who knows? "Life is like a mirror. Smile at it and it smiles back at you." — Peace Pilgrim