Dave,
Just to clarify. Are your 22 gunnels even with the dock or higher? Also , do you always tie up on the starboard side?
If your gunnels are higher then I agree with the external stairs option. I would even bolt them to your dock if you're allowed to.
If you tie up on the port side, it looks like you'd be able to step on the swim platform and then climb over? I can't remember how the step would be though....that may be tricky if you've got mobility issues.
Finally, as Dr. Bob said you need some strong handholds of some kind. But I dont know if I like the idea of putting it in the rod holder....there could be slippage and movement. I would do a through bolted setup and install 2 points of contact. Maybe one on the gunnel and one through the roof. You need to be confident that when you hold it, it will support your entire body weight if you need it.
Dave, is your weak /injured arm a permanent thing or will it improve? Good luck sir! I like your sense of adventure and your continued use of your boat. Very inspiring.