my thumbs are not functional
Glock 19. It’s the slightly smaller 9mm. 15 round clip. If that isn’t enough, you have more trouble than you can handle anyway. Or a .38 Smith & Wes (revolver) Either are great guns.
Then you’re looking at needing something without a thumb safety, so some sort of revolver or one of the new generation polymer pistols, like a Glock or Springfield XD.
Look at the XD in 9mm. You can get it in full-size and subcompact (micro) size, and the magazines interchange.
I would then probably recommend a revolver like a .38. You might have problems loading a semi-auto magazine since it takes some effort to push in the rounds with your thumb. I really can’t say for sure, but that is my guess. You can always go to a dealer and look at guns and get a feel for what works and then seek out a private sale for the same or similar gun.
Try a Kel TEC P32 they are very small and narrow and should fit deep into your hand even with limited thumb use. The 32 is enough for self defense and does not kick much. a 22 would kick a lot less but is barely considered defense worthy if at all. Ruger also was making a double action .22 revolver which is good for what you are describing.
For the larger gun try a Glock 19
I'd suggest you stick to revolvers. They're much easier to maintain. Breaking down an automatic can be very intricate. Many revolvers have fewer parts.
Then IMO get a Double Action revolver. All you do is pull the trigger and ... BANG!
Smith & Wesson still makes them (I think) or an *old* Colt, like a Detective Special, .38 spl cal, 2 1/2 snub nose (I have the Colt). You can get these for a reasonable price.
With your thumb problems you likely couldn't 'rack the slide' even on a small semi-auto like a Makarov or Walther PPK (I also have a Mak).
Good luck :-)