Passing For Normal

Damn - it's a real dilemma for you, trying to find some way through all that. Look, this is probably useless and redundant, but have you tried a MAOI antidepressant? I'm sure you have but I'm mentioning it as the MAOIs are sometimes these days seen as "older fashioned" options, however for many people they work really well. There are some major dietary restrictions with them and a few significant interactions with other meds that have to be managed, but they don't clash with diabetes that I'm aware, and they cause less weight-gain, usually. However I'm sure you tried one at some point there, but just thought I'd mention it.
And this won't be popular but I have a good friend in her forties with recurrent and intractable depression for whom none of the meds work, and the only thing that works for her is maintenance ECT. She goes in and has it as an out patient once a fortnight, sometimes only once a month, and it keeps her well. But I realise that'd be a big step.
I know I'm only talking about biological treatments here, but I'm sure you've tried all the usual therapy things and you seem to be presenting the biologically-driven aspects of your depression in particular.
Good luck in trying to find a solution, anyway.