If you're gonna use the Suboxone to detox, you have to wait quite a while for the methadone to get out of your system before you can take your first dose otherwise you could go into precipitated withdrawals. I'm not entirely sure how long but with opiates with a shorter half-life than methadone I always used 24 hours as a rule of thumb... for methadone it might be 2 or 3 days. Don't take my word for it though I'm really not sure. Just giving you a heads up so you don't end up in precipitated withdrawals.
I'd say use the diazepam the first couple days before you can take the suboxone and even after if the suboxone doesn't kill your withdrawals then taper down off the subs. The seroquil can help you sleep. You probably won't want the adderall. It would most likely make you feel worse. It is a high dose you're coming off of but opiate withdrawals aren't fatal. You can do it at home. Just make sure you keep drinking fluids and eating something (I know you're not gonna be able to eat much but try some milkshakes or something). By all means if you feel like you need help seek medical assistance but it's not entirely necessiary.
Good luck.