Doubt this is going to help, but I'll say it anyway.
I find tapering, and/or compensating for withdrawals by consuming other drugs, to be more difficult (in some ways) than cold turkey. It gives your addiction hope, that it will survive. I came off methadone cold turkey, about a year and a half ago. It was unpleasant, but at least I got off the shit. Kind of like ripping a Band-Aid off, rather than peeling it, only much more exaggerated.
If you keep using drugs to treat the withdrawal symptoms of other drugs, you might well end up taking MUCH longer than you'd like to get clean. When I start making exceptions to my sobriety, I find myself slipping towards (potential) relapse.
You're not going to like this suggestion, but here goes:
Do a massive amount of exercise. Don't go to a gym. Best not to be around people, that can trigger your anxiety. Just go for a walk. A couple of hours might do it. But, hell, walk all day if you have to. Walk until you can crash as soon as you get home. Don't reward yourself. Just sleep. Then do it again, the next day.
I'm not sure what your situation is like. If you're working at the moment, get some time. Most doctors will give you a vague medical certificate, if you're making a genuine effort to withdraw from heavy drug use. If you can't get time off work to go to rehab, or recover on your own, then maybe think about quitting your job (assuming that you can support yourself financially until you get back on your feet). No job is worth letting an addiction rule your life.
I took a long time getting clean. Played around with all sorts of different "tapering" strategies. In the end, for me, the best thing was cold turkey. The cravings won't last forever. You need to power through them and get to the other side. Addiction will tempt you to compensate with alcohol or weed or whatever, because it wants to survive (in some form).
If you're really struggling, despite your best efforts, it's better to knock yourself out - I reckon - than to compensate by getting high/drunk. If you go to a doctor and claim insomnia, they might prescribe you a couple of sleeping pills. That will get you through 48 hours. As for marijuana "not working", try eating 3-4 grams worth of edibles. Should knock you out for a solid day.
Sorry if I said the wrong thing... and sorry I couldn't be more help.
God speed.