I have recently been limited to one hand use for several months and experimented with Maltron one handed. Layout is its best feature. Otherwise, I did not like it, though it did help, and was an interested experience. Did not manage to touch type, had to pick.
Also tried mapping my beloved Kinesis Advantage so it could be used with one hand... possible, but I did not go that route, might still consider it in the future but not with QWERTY.
Sculpted keyboard might help your RSI by itself.
Regarding mice, which were the two trackballs you tried? Kensington, I bet? After decades of searching, I settled on CST. There is no such thing as a perfect mouse, sadly.
Have you considered foot mouse? I tried one, did not like the ease of use. I still have Mycestro finger mouse in my to-try list, but CST mostly meets my needs, now that I am using it with left hand. Very conveniently placed next to Kinesis Advantage, there is little wrist travel.
An interesting option might be chording keyboard, like the one I shamelessly used as my avatar.