Everybody alraedy talked about how important dps is in this game even as healer.

You said your left arm is injured and you have problems with certain keybinds, right? And you can use the mouse fine? this may seem backward for a lot of people, but have you ever considered clicking abilities with the cursor/mouse, the ones you can't use keybinds for?
I, myself, have trouble with keybinds, and apart from the first few numbers I just click all the skills. It's not top gameplay but it works well enough even for raiding, nevermind for casual content.