Working in a Belbuca routine has helped me a ton. I was a 15 year user and tolerance went so high I actually had a heart attack eventually a heart transplant. I am still on 10/325 4 a day with Belbuca (I don't use daily but subscribed 450mc two times)
32 Percocet by itself and sudden use in one day is scary, your not on a sustainable path. I understand the extreme pain but sounds like if pain management is your end game then finding the right inputs for that are in order. Sustainable is a real thing, use only goes up until the shit hits the wall. Also I just lost my brother to methadone tolerance went up so far after 10 years his blood became septic leading to other problems and passed a young man.
The short answer to your withdraw fears, If it's something you already have tolerance to, take the "Half life" of the drug X 2-4 and that's how long it's in your system. That does not mean the harm is not done during use, that's where I got it wrong.