To fix that check in the handle (you don't actually have to), just saw into it lengthwise with any old saw to square it up, and glue in a splint of scrap wood to match.
Your bow is looking fine. If you are down to floor tiller thickness, get some C-clamps (3 minimum) and a stiff board, like a 1 x 3 piece of oak or something, and crank the bow straight. No need to take out all the curves perfectly, but pull the big curves out, and get the tips aligned with the handle. All you have to do is clamp down one tip (use shims) lean the bow off to the side, clamp at the curve, then bring the handle back to center and clamp that.
Then, get some 2x4 blocks to suspend it over your stove's burner, and toast each section you can reach for about 5 minutes on medium high (mine likes the number 6). Golden brown! Set a timer and watch it. Then, let it cool, move your clamps around so you can reach the untoasted sections and repeat.
Good luck.