I have questions along the same lines. I am pretty close to the border that would put me at an unhealthily
low BF% and am also someone whose metabolism has almost certainly been damaged by years of low-calories and over-exercise. I think I've repaired at least some of that damage by doing NROL4W (and eating at or near maintenance while I did). I gained a lot of muscle, but I also gained a little fat (that's actually more recent, since I stopped NROL4W and have been exercising, but with less focus, until I figure out what to do next).
So I've read MRM and FLTS and I test as a Level 1 on the MRM quiz. Right now my plan is to do as it suggestse for that level: skip to the last rest stage and then do Metaburn. I think the most fat I can lose without going too low is 5-8 pounds, though, and I'm very worried about just winding up screwing up my metabolism again. So what I'm thinking is that when I get to MetaBurn I might do it at a slightly lower deficit than suggested - say 20%. Based on my calculations, that ought to wind up at around 500 calories of deficit per day, or a pound a week, which seems plenty fast - especially given the concerns over keeping my metabolism purring. (And yes, I am also hoping this will mean less suffering from being a little less hungry...

)
Does that sound reasonable?