Grace21, I don't think you broke too many "rules". I think you took the rules and applied them to your situation. Having a calm and pleasant-enough visit is crucial in my opinion to you very, very gently reminding H what your M was. He won't be able to handle any pressure or anything being shoved in his face - so a little visit sounds like a very good interaction. These gentle and subtle reminders will likely stay with him.
My only suggestion is to not validate his time with OW by wishing him happiness with her. It sounds like you didn't mean to. I'd suggest maybe just flat out ignoring her in conversation and only talk about him next time.
I'm glad you feel more peaceful. I know you've really been on a rollercoaster lately.
