Is there a reason he can't go to the doctor and get on suboxone for a quick taper? Or just get overall medical advice on the same questions you are asking us? It sounds like he got on the methadone for legitimate pain - he just needs to talk to a doctor and tell them that he wants off. That would be far safer.
Having said that, he should taper the methadone as much as possible and then switch to oxy for a quick taper. I can't answer your question about the methadone wds being way worse. I've never done methadone. I know the half life is longer so the withdrawals will be longer as well, but I don't know about worse overall. However, yours husband should anticipate a certain amount of pain no matter what, and mitigate if possible.
As someone said earlier, read up on the withdrawal threads. Learn as much as you can about the process and then plan accordingly. I wish you both the Best of luck!!
- VE