Could my motor skills or handwriting specifically have been affected by the results of chemo therapy?

Maybe. Some chemotherapies can cause neuropathy or nerve damage which can impair fine motor skills. Some of the most common chemotherapy which can do this woud be docetaxel, paclitaxel, revlamid, thalidomide, cisplatin, vincristine, vinblastine. There are others though so it is best to discuss with your oncologist especially if your still on chemotherapy because the dosage may need to be decreased.
Possibly. Some types of chemotherapy cause peripheral nerve damage, which could affect your handwriting. If this was caused by chemo, it should affect both sides of your body equally. If you are only having symptoms on one side of your body, you need to see a doctor immediately. This could indicate a problem in your spinal cord or brain.