4 months after major oral surgery on top of radiation and chemo and still needs pain medication: hmmn, why does that sound familiar? Oh yeah, that was me two years ago.
My words of encouragement for your Dad are that his recovery is very similar to my time frame and many others who posted here. True, some bounced back much quicker and some slower, but please share with him that it will get better before this year is out.
Christine's sugggestion to taper down with the 12mcg patch is a very good one. It is very hard to just stop the patch and switch to oral meds without extra pain and withdrawal issues. I got impatient and did just that but it was a hellish week. Better to taper down and be patient.
Again, your Dad's time frame sounds fine and within normal ranges to me.
Charm