Bill:
Wow, Im so sorry to hear of your difficulties. Its such a shame when excellent progress is seen and then you slide backwards. Its very frustrating to face the new normal. Do you use tongue depressors? I use them but not the way they are normally used. My physical therapist has me put them in each side of my mouth, not just in thru the front teeth. Maybe you would be ok with doing it that way to help stretch. Do you have alot of scar tissue?
A bite range of 16mm isnt bad at all. 30mm is great. I am back down to only 4mm now. I had gone from a 4 to 14mm and had a really bad week so went all the way back to the 4mm. Female normal bite range is 35-38, Ive been told by 2 people I may one day get to be 20mm and they said dont expect to get much past that.
I will finish my 50 HBO dives soon. Im also working with an excellent physical therapist who works my jaw with her hands. My speech therapist is helpful with working with the therabite with me.
I truly do feel your pain, lets all three not give up and keep trying

. Best of luck to both of you Bill and Carol.