It sounds like you've already/are dealing with this, which is good! I was reading an article that this is one of the taboo subjects when a spouse leaves or dies and that it actually helps when someone else even asks/acknowledges it as an issue (family and friends find it awkward to ask), so I was emboldened.
Re casual sex, I think some people get pleasure from that, but others do not. I'm in the latter category, as far as I know, but have really only had one sexual relationship my whole life. You know yourself better than anyone else, so trust yourself.
Re 50 year old dating and hook ups, I'm not the expert (have never used a dating app), but I have enough single friends in that age range that I know it does happen.
Re health, the sad truth is most Americans by their 40s and 50s aren't in great shape, so if that's important to you, maybe you need to become more socially involved with a coed group of people that are interested in fitness/fitness related activities.
Glad to hear you are happy! You continue to be a source of support and inspiration to me in this journey.
Gordie 40s W 40s M20+ kids 2016 BD W fantasy affair w OM1 I do everything wrong 2017 I start to DB W says TLTL files for D PA w OM2 2018 I do LRT W drops filing and OM2 situation slowly improving