Weight wise perhaps you need to talk to him but very very tactfully.
I will list the reasons why I decided to lose weight and get much fitter and perhaps you could use some of these as pointers when you talk to him. Incidently i am only a few years older than your guy .
1) I lost 2 dear friends to heart attacks . These guys were in my age group .At the weight I was , I would have been prone to a possible heart attack . My blood pressure was also in the amber reading .I also started getting pains in my chest which served as a warning. These dissappeared after I lost my first stone .
2) Diabetes makes peoples lives miserable and shortened the life of my father ( who wasn't vastly overweight actually) and if your overweight it increases the chan
cses of getting the disease. This is a fact .
3) I was getting out of breath just walking down the road and previously I had a very fast walking pace.
4) Fed up of buying XXL clothes . They look bad
5) Didn't like my near 40" waistline . I am now just under a 34" waist.
6) Hated being called the "Fat one" This is becasue appart from the size at the time my brother looked very similar to me .
7) I wanted to look sexy again . Prehaps more of a female trait. But I wanted to look best for my partner.
8) Body confidence was at an all time low. I didn't like what I saw in a mirror and wouldn't be seen dead without a shirt on .
9) I wanted to be around for when my son settles down and decides to start a family himself. Yes I want to be a grandad one day .
10 ) I want to be able to enjoy my retirement and need to be in the best possible physical sate to do this.
Those are just some of the reasons .
I still think you need to concentrate on the other issues first ie The fact that he has let himself go. He can still make an effort for when you go out despite his weight and his lack of sex drive . Perhaps you need to make him intersted in yourself again . Wear sexy clothes for him . Guys are very visually motivated .
As another idea for weight loss . why not attend together a Slimming World meet. Even if you don't need to lose weight yourself , you could join to keep him motivated or perhaps just lose a couple of ppound for a holiday etc. . i would ring the organiser first to see if any guys are existing members , so he doesn't feel left out in female company.
Like I aid before this isn't going to be a quick fix. For me it took over 4 years to get to the weight I am now. But sooner you strat the better.