I lost the first 40 through just primal (almost no exercise), then gained ten back with a series of weekend-only one-day binges, then learned about the leptin reset last June and have been working on that ever since. It's supposed to be 6-8 weeks, but my struggles with binges have meant it took me several months to get to the point of being able to comply with the LR protocol. I've been 100% for the last 6 weeks, and still losing in fits and spurts.
BTW, I still have all the ab muscle and almost all the arm muscle I had when I quit working out 6 years ago. I think that once you have it, and probaby partly to do with having had it for a long time before that, just the normal every day stuff keeps it up very well. I've found once or twice that just a few days of heavy lifting takes me back to about 98% with the arm strength. I have a lot of muscle hidden under the slowly receding pudge!
So no, I don't think that 6-8 weeks without exercise will cause anyone to gain weight, nor lose muscle. Do look at the signs of LR and be sure you are first, although I was never 100% sure, just fairly sure, and I think the big protein breakfast can help anybody. The LR is *not* a weight loss plan, though - the idea is to restore internal imbalances, then weight loss can come rapidly. Some people lose on it, as I have (slowly); others are still and don't lose till off it; still others gain (especially those with severe hormonal imbalances and/or a history of binge/fast where they're eating real food after binges for the first time instead of abstaining).
You may just need time! But if you have any concern at all about snack calories, I'd for sure try the BAB and see what happens. It's one thing not to snack and quite another to lose all desire to snack at all, and forget about food for long hours at a time, every day, with no effort. I. Love. It!
I ate 50g each morning for several months, then upped to 65g and found that did in my binges for good. After a month at that level, I stopped wanting to eat lunch. I haven't eaten lunch in several months, adn don't miss it at all (or the time devoted to preparing yet another primal meal each day!). Fat loss really started coming consistently at that point. I'm now finding less desire for dinner, so will probably back off my BAB soon, back down slowly to 50g daily.
Best of luck to you! And I love your goal and think I'll make it my own - one pull-up by year's end!