First off, hello and welcome to PA. I figure since nobody else as chimed in yet, i'll do my best to address some of your concerns.
Hickory can take a fair bit more grain violation than most woods, so you may be ok there, but I can't say for certain without having seen the backing. It all depends on how bad the backing really is.
I don't recommend using a belt sander or jigsaw or any power tool for that matter until you have a bit more experience. Hand tools are a much better option for a beginner, because they are more easily controllable, and force you to take your time. A good draw knife, farrier's rasp, and scraper are pretty much all you need.
Your tillering rig looks just fine to me. It's a lot like mine actually. Your bow isn't drawn quite far enough in those pics to tell much, but I don't really see a hinge yet. If its pulling 50# in the pic, then you have a long way to go. You probably should still be floor tillering at this point.
One thing that bothers me, is that the bow looks quite narrow for red oak. It may just be a trick of perspective, but it seems as though its only about an inch wide. To speculate on whether 50# @ 28" is feasible or not, I'd have to know what the back profile looks like, how wide it is at the fades, and how long it is from nock to nock. It would also help to see what the grain is like on the hickory backing.
Good luck. If need help, you'll get it. The guys here at PA are great. All you have to do is ask. One last piece of advice though; you'll get more answers more quickly if you ask specific questions.
