I see two very good things happening here. Your H wants to stay in MC and it seems that one session was a good vehicle to get you and your H talking.
I know you know this but one session is just one session and it is not surprising he feels negative about it. C'ing is hard and a very deep/emotional process and it can be draining and eye opening which IMO naturally leads to negative feelings.
I am not sure I really buy the whole 'soul mate' ideal. Sure, I do think some people are better suited than others but I don't think there is just ONE person out there for all of us.
Long term R's versus short term R's (lust) are much different. I think in long term R's love changes as time passes and if you don't work at certain things the love can change to mundane. When two people are consumed by LIFE (bills, work, children, running a household, family and so on) the R changes. When you talk about "high school love" well, it is very easy to have nothing but lust when there is no "real life" issues to attend to.
That IMO is exactly why affairs are so filled with lust. It is all a fantasy with no problems or day to day "real life" issues to deal with. The two affair partners don't share things like bills, children or a house so every bit of time and energy can be focused to the affair and that alone, that escape, is a lustful image. Who wouldn't want a highly charged sexual R with NO problems and no real life issues to deal with?
I posted this on another thread but I have a lifelong and dear friend who is going through sort of a rough patch in his marriage. His wife is a terrific person and they love each other and there is no talk of separation but things have gotten mundane after 10 years. They both commute and work very long hours, they have a little girl and after working and tending to their daughter they are simply exhausted and sort of going through the motions. They both say they want that "fire" back but just aren't sure how to get it.
My H is still with his affair partner and has been for 2+ years and their R is very much what you described with your H and his OW. The drama, the breaking up, the fighting... really immature stuff. I am amazed my H tolerates it because he hates drama and fighting (or he used to, lol!). In a way I wonder if that sort of adds to the "fire". Stability in a R is a good thing as long as it is not taken for granted.
I am sort of just babbling here but I do think you and your H have made some very good steps even if you feel they are twinged with negativity. C'ing is not comfortable so many people do feel negative about it. I think it's pretty common.