HI LWM and Welcome!!
I had the nerve/muscle biopsy in June and that diagnosed my Chronic Axonal Neuropathy.
My dr. said it's very hard to find a good surgeon to do this biopsy and he has only one dr. he trusts to do it now. He said so many times when a biopsy is done the tissue/muscle/nerve isn't properly prepared for the trip to the lab and then they can't use it! So you might want to ask if this surgeron has done a biopsy before and his success rate!
My biopsy was done behind my ankle bone on the back/outside of my left ankle. I haven't been able to wear reg. shoes comfortably since the surgery, only able to wear sandals.

I think it's just the location where it was done that caused this, BUT I wouldn't have been diagnosed if I hadn't had this biopsy so I'm glad I had it done.
I hope your husband gets all the tests he needs to get his PN under control.
I, and many here on this forum, get IVIG infusions weekly to help with PN, maybe your husband will qualify for that also.
Keep us informed how y'all are doing!