Example: I have a kid, I'm gonna buy a harness so that I can lift him with one arm when my wife needs help.
Wishing you the best for the future!
For emails, tell people about your arm issue and ask them to have some patience with you. Try and use voice tools to write out messages where you can.
Depending on what kind of programmer you are, try and focus more on the things you can do without much impact: perhaps planning and diagramming out systems on paper, doing research, or doing some graphics related work.
Hopefully your arm is ok.
Make sure you can enter your important human memory only passwords with one hand, sometimes that's harder than it would seem.
For real writing (emails, slack messages etc), I'd say dictate it and then just use your keyboard for edits.