So many questions but does he know how you feel? How long has this been going on? Have you tried to go together for help?
Always sad when a marriage breaks up after 25 years.
Suggest you communicate and do everything you need to do to try to save it. Let him know exactly how you feel and how serious it is.
If it still doesn't work out then you'll know you tried and not have regrets later.
No one is perfect and the grass is not always greener. I know, I've been divorced 14 years still trying to find the one and find the one. Sometimes that "one" is in your own back yard.
Life is short and you both need to be happy. When the sex stops then that's a red flag in my book unless there is a health issue.
I left after 16 years. Very similar reasons. You are entitled to be happy. You didnt mention if you have kids? Ask yourself where you will be emotionally in 2 years if you stay. I made the mistake of going straight into another relationship and falling hard. I am only now going through the phase of finding myself and being on my own, but I know that there is a whole world out there. You rather be on your own than chronically unhappy.
It is hard but you say you have loved ones around you to support you - that will get you through.