Hi Op,
Firstly, I think that his almost immediate attempts to have you lose weight were not fair, he shouldn't have been with you if he straight away wanted to change you.
That said, time has moved on and there's much more awareness about how the sedentary lives we lead are affecting us and the long term issues that can be caused. It would be a good thing to get close to the so-called "normal" for age, height etc. because health issues can be avoided. Being a diabetic is no fun, i know a few and they hate it.
So if you are going to lose weight, do it for that reason, and not for him. Do it because you want an active life with your kids and no health issues catching up with you over the years.
You said you hate the gym. Gyms really aren't necessary. We all do so little in the course of a normal life with cars, lifts, etc. to move us about, and with high fat foods in plentiful supply, it's no wonder people struggle with weight. Almost everybody I know who's had any success with maintained weight loss has done it by being more active rather than sticking to a diet. So instead of getting on a diet plan, why not get on an activity plan instead. Check out things like fitbit (google it) and use the very active communities on those places to get some support.
As for the financial side, I don't think you should hand over full control. You could go instead for full transparency. So you could have cards, accounts, etc in your name, and open, manage them, and close them as you please, just offer to always be ready to show the state of them.
I think that's a nice meeting-half-way position. It doesn't relinquish control yet it shows you understand that in marriage the financial position of one is of interest to the other. It's astonishing that people can take the view that because you ran up 30k of debt but managed it down yourself, it's your business. If something happened to you and you were unable to work, or you died, and all sorts of scenarios in between, that debt problem would very quickly become his. I can understand why he wants to know.
Good luck.