Welcome to the site!
I would think that the hands-on experience at the gun club will be invaluable in your case, so you can get an idea of how each gun feels in your hand, and whether or not you think you'll be able to control it. Unfortunately, powerful calibers (that hopefully won't take many shots to stop an attacker) usually have more recoil and barrel bounce/flip than the less-powerful calibers.
I would encourage you to select a gun and caliber that you can shoot well, even if it's only a .22, over a more powerful gun/caliber that you shoot less-well. Shot placement (hitting your target in a vital zone, even under less-than-perfect conditions) is one of the few things that most folks agree is absolutely critical, when discussing the relative effectiveness of various guns and ammunition in personal defense. Whether you're target shooting or defending your life, misses don't count.