Ruby, glad you're in counseling and wish you the best. Since the affair was "long and complicated," I imagine there are a lot of "little" betrayals to get over inside the "big," overall one. The fact that dh got involved with ow in the first place, some of the special things they did together, lies he told you to cover up, maybe a few times when he tried to break it off but then didn't, etc. Idk how counselors deal with this, but I imagine you'll have to work through some of these separately.
Some of the hurts may never fade away completely. Both you and dh will have to live with that if it happens, I guess. But I hope you get past it all and move on.
I appreciate that there are things he does with/for you that he never did with/for her, and I'm glad you appreciate it. Would it help, also, to start building some new experiences together that aren't tainted by his affair? Maybe go on a vacation somewhere neither of you has ever been and learn about it together? Or start to volunteer together for a cause or organization that you both care about.
Anyhow, best of luck moving forward!