Any news from the solicitor?
I think you do know what you want, and what you want to do. It's not your weight, it's his whole attitude to you that's wrong. As you yourself say, you're bubby with others, and depressed with him. What does that say? He's toxic to you. He's got his good points, of course, but not in relation to how he makes you feel. You shouldn't be rationed for affection, passion, sex, whatever, you should be able to give and receive them in equal measure. He obviously has a very low sex drive, and that may suit some skinny, chocolate hating woman out there who will be the love of his life - so you owe it to her to set him free !!!
- well, that's one way to look at it, anyway.
And I agree with the others - you'll probably find the weight drops off once you're free and able to become yourself.
My exh had a low sex drive - we only did it once a week when we first met (never on weekdays, because we had to get up for work the next day, wtf! - then it became once a month, and after dd, never again - and in the end it drove me into an affair. I should really have tried to deal with it without the affair, but I'm not perfect and I still carried a torch for dp, so it was sadly easy to slide into things with him. Like you, I didn't marry with that intention, I deplored extra marital affairs. But since exh and I split, I'm SO much happier, and feel like I'm truly myself, inhabiting my own skin, for the first time in my life. The only pity is that I was 45 before that happened. It WAS scary, sorting out the bills and things alone, but I feel I've grown up a lot in the last 5 years.
It's never too late, and you're probably not even half way through your life. Seize the day!!