Edit: Blood pressure pill, do you refer to clonidine? Yeah, that might be worth a try too, forgot about it but will make you lazy/sleepy/tired and sometimes without actually sleeping..
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Maybe memantine could be of help for you. It's sold for Alzheimer's and is a bit disputed for this diagnosis, but independent of that it offers interesting pharmacological properties. First, it is a dopamine agonist, that should help a bit against dopamine depletion / overabundancy of receptors induced akathisia. I know this symptom from psychopharms and it's hell.. Second, it's a "low-trapping" NMDA antagonist, that has been used by some with success to lower tolerance to stimulants. Also NMDA antagonism does its own to make some things more tolerable, for me the stronger ones are the best anxiolytics I know of, memantine unfortunately isn't very strong in this but it depends on person and condition, might still help.
Depending on where you live, it will be more or less easy or hard to get. Don't let them reject you cause it's "too expensive", in many places exist very cheap generics and with a prescription they can be ordered too. If really not, you could try dextromethorphan (this, too, has helped quite some to lower tolerances) but carefully as its noradrenergic and could maybe cause initial worsening (unsure about this).
I would really try to absolutely minimize use of benzos as they are, as you probably will know, addictive on their own. Especially in such a situation where excitation vs. inhibition in the neuronal system is out of balance, I wouldn't mess with them any more than required and blacking out yet without help sounds like a road to hell to me.. That said, not everybody gets always problems, I for example aren't overly sensitive to BZD tolerance despite having anxiety issues. But once, in my teens, a doc managed to crack that line by having me on 2-3mg lorazepam per day for maybe 90 days, then was moved to another hospital and they stopped cold turkey. In that already stressful life situation the additional decrease of what I'd call "fear/panic threshold" akin to "seizure threshold" was hellish and required around 45 days to fully recover from insomnia and panic attacks.
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Another med/s that come to my mind are pregabalin / gabapentin. They are a bit different from the benzos, even when the overall profile of effects might sounds pretty similar. Certainly (for me) they are much less dependence forming, tapering down over some time (few weeks) was enough to get off >600mg/d for months without really noticing anything. They might help you more with the akathisia, but that's now more of a guess than with memantine. From experience you can combine them, memantine + pregabalin. If you have a stable dose for some days, you can even take --little (! potenciation !)-- of benzodiazepines as/if required.
If your problem too is being unable to sleep - weird cause I usually just slept over any sort of stim withdrawal but also I was never really using meth and didn't escalate dosages as much as many do.. you might try the old "drowsy" antihistamines like (will put name later, forgot right now..) or diphenhydramine, the former actually made me sleep while the latter failed. It's the same mode of action as many of the modern psychopharms use to make you sleepy, like that horrible practice of abusing the side effects of antipsychotics as sleep aids.. so you can also go get just the "side effect" without the non-required toxicity.. You -don't want- antipsychotics in a hypodopaminergic state.
Here I know too little, maybe taking L-Dopa might help akin to 5-HTP with MDMA, for example. Just don't use combination products with a carboxylase inhibitor, or if you do, use very little, like 1/4 of the min dosage first and check how it affects you. These inhibitors make the supplement like x100 stronger as without the majority gets broken down in the stomach and becomes inaccessible to the brain.
BUT probably it's not really too less dopamine but too many of those receptors, this just needs time. Feeding them will inevitable prolong the withdrawal but can make it much easier to tolerate, so it's a mix calculation. Memantine can induce PAWS dopaminergic withdrawal too but it's seldom compared to other dopamine agonists so I'd prefer to stay with the memantine .. I was on 30-40mg/d (that's twice the recommended dosage, but that one's also for Alzheimer's. It's a pretty safe med.) for 7-8 months or so and again some stupid doc had to think I'd be addicted and put me cold turkey. Had symptoms but nothing of classical dopaminergic withdrawal. Indeed I developed a hypomanic episode.
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How was your last usage pattern, how much / how often?
With psychostimulants you can of course also substitute for psychostimulant withdrawal. If you have a decent scale, make capsules (! to get away from the rituals and the instant hit.. I know, I know.. I too like things to hit instantly.. but really it's part of the whole addiction thing. Lisdexamphetamine for example, taken by mouth and with a slightly delayed onset, is less habit forming than plain dexamphetamine, and that by mouth is less than snorted..) of the minimum amount you need to not feel bad. Take them for dunno.. 5 days, then go one more step down ... Can be combined, carefully, with memantine / ev.pregabaline, imho.
Good luck..!
