I belong to a local range that requires NRA membership but they allow visitors as long as they are accompanied and monitored by the member. If you knew someone who belonged to such a range you might be able to accompany them as a guest.Hopefully that someone would be a good instructor. Your physical issues with your hands are problematic. Controlling a pistol requires the use of the thumbs to grip the pistol properly. I would recommend a pistol that produces the absolute lowest recoil, even a .22 is better than nothing and certainly better than something you may not be able to control. Calibers go up from .22 to .25, .32, .38, 9mm, .40, .45 etc. For you the biggest gun you might be successful with would be a 9mm. I read something recently about one of the manufacturers coming out with a .32 magnum also.
The .327 Magnum is the new round you’re thinking of. I’ve seen Ruger and Taurus revolvers chambered for it.
The thumb-joint problem is a challenge...
.32 H&R magnum - I have a collectors S&W model 16 in .32 mag. It’s a mighty snotty little k-frame. BATFE now classifies it as “curio/oddball”