This all sounds quite familiar to me, I was in a similar position some years ago, the points that resonate are that I can be quite sensitive and emotional, and my partner was very rational and independent. There was always a spark, and we loved each other hugely, I guess I wanted a softer more understanding partner, I think she wanted someone who was less emotional and less sensitive, so we did split, at my request, 10 years on, we are both still single, we still see each other, we still love each other, she has softened, I have become less emotional and less sensitive, I never stopped thinking about her every day, and although I came across women that were soft and emotional and sensitive, they lacked other things that she had, and I realised that just one facet wrong out of hundreds that were right should not be the be all and end all.
However, looking back, if someone had explained that to me 10 years ago, it would not have made any difference. It's hard to put into words how something on paper can look so great but feel so bad, to the point where you want to call it a day, but I can understand that, because it happened to me. People, on the whole can't change, you cannot magically become more or less sensitive, or understanding, or rational, or independent, if I was talking to myself 10 years ago, I would suggest a short trial separation, because it would very quickly indicate whether the choices you are about to make feel good, or feel bad, for both parties, and go from there, sometimes you have to lose something, before you realise how good it actually is.
20 years together is a long time to build up frustrations, not everyone changes at the same time, in the same way, sometimes you have to play catch up, and that can feel like end of the world, I don't really have a solution, but the grass may not be greener for him on the other side, it certainly was not for me.