Yes, I'm. - not a usual sentence. --> Yes, I am. (Also space after "." and ",")
No I'm not.
I'm is a normal use experession, if informal. If your writing something informal, then I would not be afraid to use such normal contractions.
If you are wrtiting something formal, then yes, I'd also skip these, for the full versions. I'm not sure that everyone form every culture will agree, but that's the answer for me, where I am.