Two things helped me. First is easiest to explain: cutting back or eliminating caffeine. Seriously. And my carpal was fairly bad, so I know what a troubling (literal) pain it can be. I found it was made much worse by my 4 cups a day habit back then.

Number two is more complicated to explain, but it is a mighty powerful keyboard skill that can sometimes go a long way to reducing the "awkward reach" keystrokes. Specifically, copy and paste! Read on:

(TLDR: learn Ctrl-Ins, Shift-Ins, and Shift-Del, maybe. Instead of Ctrl-C, Ctrl-V, and Ctrl-X):

In the past I often found myself doing long sessions of paging up and down documents and source files, and doing complex copy and paste actions, for reasons. Ctrl-C and Ctrl-V were not so awkward on the original IBM-PC keyboard, because Control was right where it should have stayed, ha (where your CapsLock key is now.) When they moved it to the lower left and lower right spots, it made it a tough reach with just your left hand. You could learn to do RightControl + LeftC for copy, but I never did. Instead, when I need to do a lot of copy and paste with paging up and down also, I get my right hand at the home position on the (full sized) numeric keypad (in arrow mode not number mode), and I get my left thumb and forefinger on left shift and control. Then PgUp, PgDn, Home, End, Ctrl-Home, Ctrl-End are all lightning fast. But most importantly, and the point of this rant, LeftCtrl + NumericKeypad-Ins is COPY, LeftShift + NumericKeypad-Ins is INSERT, and LeftShift + NumericKeypad-Del is CUT. I have never met anybody that could do cut, copy, and paste faster than I, in a long career, if I must say so. Try it for a moment, your fingers barely move when you learn the technique. But I never could talk more than one or two people into learning the skill, much to my disappointment. And now I'll probably never do any long sessions like that again (because AI mostly like you said), oh well.