Crud, I didn’t see this thread until I posted on the other one; so I’ll just C&P from there and add and edit a little.
If you’re still open to the idea of a gun, a pistol chambered for the .380 ACP cartridge isn’t the worst way to go. It’s no powerhouse, but it’s more tame and doesn’t blow the crap out of your eardrums as badly as more powerful cartridges do. It’s mainly found in compact pistols, but it might be worth looking around for a larger and heavier (albeit uncommon) example, both to keep it tame and (relatively) quiet (longer barrels aren’t as loud as shorter ones). The longer barrel also gives you a little more power (because the bullet has more time to accelerate before it’s out of the the barrel) and a little easier aiming.
All depends on whether you think it’s something you’re prepared to work with. What you might do is go somewhere to an indoor range where you can rent a pistol to try out, remembering (among a lot of other things) that you won’t be wearing hearing protection in a real emergency.
As to the felony conviction, what others have said. Can you vote? If so, it may already be cleared. But you should check and make sure. If it isn’t, the only thing you can do is try to clear it (I imagine that means petitioning a judge; not sure at what level, but I’m guessing state).