If you go with Crosman Custom Shop, you get in the club, and can order custom shop parts eg. barrels breaches etc. when the need or urge arrives.
First, Hotlead, our prayers for full recovery are with you.Second, after thinking through the motion movements for my CO2 and multi-pumpers (2400KT; various replicas; 1377; Daisy 880, Crosman 2100), I'm not sure that you will not get frustrated trying to do some of these things with just your one hand. For instance, I cannot pump the Crosman 1377 without both hands--and that goes for the 2100, as well. Now the Daisy 880 is gentle enough to cradle it to my chest and pump about 5x. Loading the 12 gram cart in my 2240KT is very doable with one hand dominant; but cocking and loading it might be problematic with just one hand. Mine has some backward resistance that takes some coordination.Hence, might I recommend a two stage process. First, buy an easy to load (cart and pellets) CO2 pistol and learn how to shoot accurately. For this, the Crosman Vigilante might be ideal (but it's loud). Mine shoots in the 400s fps, and can easily reach out to 10-12 yards (maybe more, but I don't try that). Loading requires opening the breach and pushing down the barrel and then re-filling the faux cylinder clip with pellets, while the clip is laying flat on a surface. I have no doubt this gun can kill a bird at shorter distances; but, I'm not sure about tree rats. I do know that it shoots with more authority than my P-17 (which is not a candidate for you now), and I use the P-17 to finish the kill on wounded pests. It will penetrate a skull out to about 8 ft. Second, after you've become proficient, then buy a higher fps pistol that will reach out further. Perhaps the Diana Chaser will suffice for all this. I looked hard at buying one last year, but I have break barrels for the longer shots and love these lessor pistols for short shots or plinking. Don't get discouraged; do get what you want and have fun trying!!!!Archie
A 2240 is a good base for a pistol... but to mount any optics you need to buy a steel breech kit.You can buy those "barrel pinch" mounts for Crosmans but they are not known to be reliable. Also, I do not know if your right hand has the deterity required to install a steel breech, there are some tiny screws involved.