Have you considered the loco/bdiddy approach to dieting? Just super clean eating and cold turkey from alcohol for as long as you can make it. Moderation doesn't seem to be working all that well for you. I mean it has worked inasmuch as you've lost a good amount of weight over time, but I'm not sure it's working well for you psychologically. These binge days seem to make you feel awful about yourself and spiral more and more bad diet days.
I've read that leg extensions are terrible, so yes, probably shouldn't do them. But let's not forget, I don't give a hot **** about being strong or any of that, this is all for aesthetics...to attain quality poon, and to more appreciate having to look at my naked body...that's all. So useful in terms of that might be different from your usage of "useful".
Nope. I think I mean "useful" by just about any definition of the word.
Do lunges/reverse lunges, Bulgarian split squats, front squats, step ups or just about any other lower body movement which involves knee extension.
You'll get as much quad development from any of those as you would from leg extensions, plus you'll probably burn more calories doing any meaningful volume in any of them as you would from doing leg extensions, plus you'll probably get some extra glute + ham work in. Wins all round.