Opioid addiction is interesting because the body can adapt to greater and greater amounts, apparently without limit. You mentioned a daily intake of 120 mg of oxycodone. I know someone who worked up to 1600mg daily, what a special kind of hell that entailed.
The terror that we all felt facing a future without our drug of choice can be viewed simply as the terror our addiction feels being deprived of its buzz. To that I say, bring it. You are in charge of your drug intake, and capable of staying straight for good. Congratulations on that commitment to yourself and your future life free of this miserable stuff. Well done.