Sorry to hear that. I have a long list of major things that were already enough to warrant the need to be on opioid medication for my pain management. And then I was diagnosed with primary progressive MS.
Prior to this long process of elimination to arrive at MS-- I was just fine with the 50mcg fentanyl patch and hydromorphone 8mg tablets x4 daily. This was in combination with my epilepsy meds - Klonopin since age 7, titrated up over the last 40 years to 16mg daily. Pregabalin capsules were added after I had an aneurysm burst in my brain causing a subarachnoid bleed and subsequent series of 3 massive hemorrhagic strokes. Pregabalin was after a long list of other ASMs which were either ineffective, or intolerable. Keppra, Topamax, Zonisamide, Carbamazepine, and many other 2nd & 3rd generation ASMs (not to mention all of the 1st gen & early 2nd gen ASMs I had already been tried on throughout my childhood, teenage years, and as a young man such as phenytoin and phenobarbital).
I mention this because of the fact that pregabalin helped me with my pain as well as quieting down the seizures.
Additionally, a muscle relaxer has been a great tool for my pain management. I currently take Baclofen although I have been on Soma which worked well for my muscle spasms and cramping, along with the strains I get by trying to do most basic need-type of things that are okay one day, and then gone from my capability the next.
As far as the fentanyl transdermal system and your husband go, I can say with absolute certainly from my 19 years on the same thing, times-tolerance is a very real thing that is humanly unavoidable unless a person doesn't wear the patch and/or take their dosage in full, every single day, and never stop for more than 6 months, with the outcome being a substantial difference with that duration increasing to years, and even decades. *Some people, a very small percentage are given the gift of never experiencing this, but that percentage is less than 1 in 10 Million. And there's no data beyond a very small abstract study with less than 150 people who were actually able to be monitored consistently over the 36 months of the trial.
The 2nd thing that is definitely a factor in your husband's case is the insanity of the changes in the overall amount of medicine that each system contains. This used to be fairly uniform: 100mcg patch contained 16.5 mg of fentanyl. The amount began to fluctuate by the manufacturer, and different manufacturers were and are still, not created equal.
Sandoz, Teva, Mylan, and Mallingkrodt were leaders with the better quality matrix formulas. However they have been discontinued - and the alternatives are not the same. Each one I've found has 10mg per system for the 100mcg, 5mg for the 50s 2.5 for the 25s etc. And that's a huge deal! Not to mention, I uses to get stuck with different types whenever the pharmacy got a different type - until I would go through withdrawal as a guinea pig to find a new one that worked for me without burning my skin or something else wonderful like that, and then have my doctor write, "Dispense as written" wjth the name of the one that worked as "medically necessary" and list the ones that were caustic as, "Do not dispense, Severe Allergy" or whatever the doctor and my pharmacist said to use for language to be placed in my file as an electronic note that throws a red flag if someone accidentally tries to fill with one of the bad ones.
Anyway, all of this information is available on this site and the FDA site drugs.com -- forums going back 20 years with real people like myself in a Q&A discussion format, as well as reviews on each medication with the reason why each person is taking it, for how long, and so much other content related to...

I hope you and your husband are well, and that my mini novel here while I am in too much pain to sleep, proves to be of some sort of help to you.

Take care,
Michael