Jen, I have always liked the sound of you from your posts. You seem like a down to earth of person who I would probably get along with if by some incredibly unlikely event we met in real life. For me, that's high praise as a lot of internet people I envision giving them a good smack instead.
The weight gain from pred can be brutal. I went from being pretty underweight to overweight in the space of about
a year. I lost a little of that weight after my first surgery, but it wasn't until I had a second surgery and subsequent flare-up that I lost even more weight. I'm not underweight but not overweight anymore - at least not technically, although with my belly fat I feel like I am.
I do believe that for some people it's incredibly hard to lose weight because their metabolisms are so slowed down. Sure, if you can subsist on 800 calories long term you would, without a doubt, lose weight, but that isn't a practical way to live for anybody who isn't an anorexic (or literally unable to eat for other reasons).
For more sustainable weight loss, it's better to go slow rather than fast and incorporate some exercise as well. You can work out your daily energy expenditure here:
/tdeecalculator.net/Don't go more than 500 calories below your TDEE if you go on a diet, otherwise you risk making your metabolism crash and burn even more.
That all said, it's perfectly possible to be overweight and healthy: there is some evidence that mortality rates from various diseases are lowest for those in the 'overweight' BMI range, i.e. 25-30. Conversely, having a BMI in the 'healthy' range of 18-25 doesn't automatically mean you are healthy at all. This sounds like stating the bleeding obvious, captain, but I do think there are many, many people (including doctors) who equate slimness with health and extra poundage with unhealthiness.
Meanwhile, your husband has stayed with you for 20 years. I'm sure he'd rather be with you than with anyone else. I know there are some men who only want the trophy wife hanging off their arm, but I don't think most men are like that.