It sounds like the marriage has a lot of difficulties. Sexual attraction, over the course of a very long marriage, shouldn't be the only thing that binds a couple together. You need to have fun together, have some shared interests and projects.
I'd have a proper talk with him. Say that this isn;t working and that you want to discuss the options for a better life for both of you, including separation or divorce. You need him to understand this will take effort from both of you.
I'd start by trying to rekindle some of the interests you had together - could you go to a gig of a band you both loved when you first started dating? Or a comedian who makes you both laugh? Or a talk by someone you both admire?
Maybe go on a hike together - train to climb one of the three peaks or do the coastal path or a part of the camino. Discuss places you'd like to go and jointly plan a holiday. Rekindle the fun and companionship of a long marriage. Make each other laugh. Discuss what you hear on the radio - from politics to documentaries. Ask him to cook with you.
Tell him of some changes you plan to make, including no longer being the family skivvy. You both work, so together make a list of all jobs that need doing daily, weekly, monthly, seasonally and share them out equally, with some being done jointly. Don't make this a punishment, Just be calm and direct - this isn;t fair and it is going to change.
As to your looks - what matters most is how you feel about them. If you don't feel sexy and confident having gone grey, you could colour your hair. If you want to lose some weight because you'd feel more yourself, do. Otherwise keep going with the strength training. You could work out at the gym together. I sympathise with you - AD medication just piles the pounds on some of us, and then menopause does the same. I was the same weight all my life, bounced straight back after both pregnancies. Then started taking ADs and the weight just piled on and never really left, even after I stopped taking them.
I agree with a PP that his diet comment might have been a snipe back at your viagra comment. Men are as sensitive about their prowess as women are about their weight. It's worth trying to chat and build a more enjoyable life in total - not just sex - before giving up on a marriage. It sounds very stale but that could be salvageable.