You should get a DEXA scan... otherwise you're just guessing at what the problem is, and that's if there even is one. You can usually buy a package of 4 or 5 scans for a couple hundred bucks, and clinics that provide scans are everywhere these days. Just Google "DEXA scan near me". A DEXA scan will tell you what your fat mass, muscle mass and water numbers are. The first scan will serve as your baseline and then subsequent scans will show any changes from your baseline. That way, you'll eventually know if your weight gain (or loss) since the first scan was actually muscle gain, fat gain, or just water weight. It's actually a pretty fun process to go through, and subliminally, it encourages you to keep working out and eating right so your next scan will be better than the last one.
Have you ever considered where that collagen comes from? Specifically? If I'm not mistaken, it's whatever is left of the animal after the meat and hide are removed. All the gory and unsightly stuff squeegeed into a corner for "processing" before the floor is hosed down. In any event: https://www.health.harvard.edu/blog/considering-collagen-drinks-and-supplements-202304122911#:~:text=At this time, there isn,be absorbed through the gut.
That's not Mentzer. If you want to familiarize yourself with his work, you should consider this book: Just don't bother with the "consolidated" routine. But 5-6 days a week is too much if you're training to or near failure, which you should be doing for the best and most efficient results. This is also a pretty good book on HIT: Although Darden's claims are exaggerated.
It raises your metabolism and keeps it there for a while even after you completed your workout. Also, the more muscle you have, which you can only build with resistance work, the more calories your body burns while at rest. But, yeah, diet is key.
Btw, you can't spot reduce fat, so doing ab crunches doesn't really help you much with the sixpack. It's a common misconception and why many people waste their time at the gym on doing ab crunches. Training your abs will make them more prominent (just like training any muscle), but it doesn't burn fat in that area, unfortunately. Pretty much everyone has a sixpack (except The Rock, lol) but it's just hidden under layer of fat that needs to be burned to reveal the sixpack.
Yeah, I bought a bathroom scale that measures body fat, body water, and several other factors, but I have doubted its accuracy. It's hard to believe that a bathroom scale can derive all that information from standing on a scale in your bare feet.
I had one several years ago, but it's missing in action. But then I weighed about thirty pounds less...... 150's