Regular users can't PM.
If you are taking off that little material, staying at 220 should get the job done on clean belts. If you are hand sanding, may wanna stroke it with the file a bit, then clean it up. There isn't much risk staying that thick pre-HT, there is risk if going too thin however. If you aren't having it professionally done, I'd stay where you are at.
Warping occurs due to uneven grinding or stress in the steel. Check for evenness prior to HT as it is critical. And fractures on a thin edge occur from too quick a quench, not necessarily just the thinness. But thinness is an attribute of quenching speed, therefore staying a little thick doesn't hurt. If you have done it enough, you starg to get a feel for how thin in what steel will quench in what quenchant at what temp etc... Hence why the pro's rarely pooch a blade.
It is a nice knife design. Very well done so far, it should prove to be a good useable blade. And I take from the username you are a fellow bone huntin critter gitter! The blade you have there should be good for dressing, skinning out, working the chest and even light quartering. Nice.
Cheers!
-Eric