How do I get rid of the “today is a loss, might as well keep overeating because I’ll start tomorrow” mindset?

I used to be 350...

How long were you 350 for, and what was your weight like as a kid? Theoretically it shouldn't take getting back to that size to fully restore LBM, but I'm neither a doctor nor a nutritionist. For what it's worth though I'm an inch shorter than you and my weight gain capped out somewhere around 190lbs. That was back in December and I'm on the low end of 160 right now with 150ish being my pre-ana weight.