Well I'm glad it's not that fentanyl. Deadly stuff.
I doubt methadone would be a good move. The acetyl ester of R-4066 is x212 M and lasts for 3 days. That would be appropriate foe you. It's legal but one of the precursors is costly. I can send you the synth.
Almost everybody ending up with an addiction thought the same at first. I think propaganda telling one would get hooked instantly on drugs after the very first dosing is to blame for this.
your a smart guy but Im giving up on opiates as they have now ruined me twice and I cant handle the withdrawals. Id rather be in pain 24/7 then have to go through the withdrawals.