hair loss is another thing that most (maybe all?) of us vets, in retrospect, wonder why we worried so much about. It's temporary - and for many of us, we're the only ones who notice the loss (I know some people lose a lot - a very noticeable amount - but most of us don't). It's a minor annoyance in the grand scheme of things.
whether or not you need Spanx depends on where your loose skin is - and how much you have. I was apple-shaped, so I don't/didn't have much on my hips, butt, and thighs. Mine was almost all in my gut. And yes - I just tucked it into jeans or "tummy control" leggings, and always wore a slightly oversized, long-ish top. Ta da! Excess skin gone. I'm sure I was the only one who noticed it. Spanx would work, too, if you're not wearing something that it can be tucked into.
as far as 500 calories, that's really just the first month or so. From about that point until maybe a year out, I was eating 600-800 calories a day, usually closer to 800. At around the year mark, I was at around 1000-1200. Now, in maintenance, I eat 1500-1700 a day. I did develop what we think was reactive hypoglycemia at about two years out, but I was told to eat something every 3-4 hours and, if I eat a carb, to be sure to pair it with a protein. That seemed to take care of it...