For a number of years I had a similar mindset - I really really really didn't want to leave behind a body I wasn't satisfied with? I'm not sure how to correctly articulate the feeling but despite being acutely aware of the fact I'll CTB eventually I just could not and would not let myself CTB before I started transitioning, at the very least. Even now, everyday I work on my body and transitioning. Which I suppose I recognize as a bit weird given I'm at three attempts, I just - so long as I do live I have give transitioning my all.
I realize I may have deviated a bit from the intention of your post, it's just I do see a bit of myself or past self in your writing. Though it pains me to hear about your social circumstances (I hope that's okay to say, not sure how to navigate this sort of thing on SaSu (>人<;)) - I'm more fortunate in that regard, so for me it was more I guess about leaving a body behind I was satisfied with? Or like I tried? Though in a similar vein, albeit a different approach I did always think a closed casket funeral would an appropriate end too (hence attempting train CTB). I would just imagine the catharsis of final being able to take out my frustrations once and for all on my body - I think to a lesser degree this drive also fuels my SH.