Well, I'd like to help you with your sleep because I can easily sympathize, but if you've really tried all that and nothing else has worked then... phenobarbital it is. Just in case, I'll give you a list of all soporific/hypnotic drugs/supplements available that I can think of off the top of my head (excepting benzodiazepines, barbiturates, quinazolinones, z-drugs, unattainable GABAergics (etomidate, propofol), and alcohol):
Carisoprodol
Meprobamate
Mirtazapine
Trazodone
Cyproheptadine and Amitriptyline and other classical tricyclic antidepressants
Paroxetine
Lamotrigine (Not really recommended)
Phenibut (Relatively short, but truly horrific withdrawal syndrome if used long enough.)
Baclofen (ditto)
Muscimol (Shoddy, ungainly efforts based on cursory research to promote the conversion of the ibotenic acid in Amanita Muscaria mushrooms into muscimol could lead to excitotoxicity which is something someone in your position really doesn't need. GABAergics don't really seem to work that well with you, anyways, but I thought I'd include for the sake of completeness.)
Diphenhydramine and dimenhydrinate (neither of these comes with any recommendation at all, but they will facilitate sleep, albeit non-recuperative, troubled sleep from hell)
Agomelatine
Tasimelteon
Ramelteon
Melatonin
Taurine
Magnesium (without calcium)
Pregabalin
Carbamazepine
Topiramate
Edit: Beta and alpha blockers are pretty soporific, although they won't necessarily (and probably won't) enhance sleep quality. These are not to be used with any other central nervous system depressant, by the way (for that matter don't mix them with anything, if you don't know what you're doing). Clonidine and guanfacine are better choices than selective(-ish) adrenergic receptor antagonists. I recall that when I first used clonidine it made me very sleepy.
I found after a good deal of experimentation that the combination of pregabalin and mirtazapine really knocks me out. Unfortunately, the combination has a very funky synergy and I always feel awful and depersonalized the day after using it. Mirtazapine in one study - although I do not know by whom it was funded - was said to "normalize sleep patterns" supposedly (semi-)permanently increasing length of time spent in deep stages of sleep when used over a period of a couple weeks in patients with insomnia. I don't have the study on hand and don't know where to find it at the moment. My current sleep regimen is 3 mg of melatonin (start with one; people typically find lower doses more effective than higher), taurine, magnesium, 150 mg of pregabalin and possibly a small amount of lorazepam. I don't feel that well-rested but at least I'm not going crazy from sleep deprivation.
Divalproex, I've read, decreases the activity of GABA transaminase, increasing levels of GABA. Pregabalin on the other hand - and this is not particularly credible information - upregulates translation of glutamate decarboxylase, again increasing GABA levels. I don't really recommend that you try combining them (I don't know of any specific negative interactions but my intuition tells me that there could be a great deal of them). I don't really even recommend that you take divalproex alone, but it's something to try if you run out of options, I guess, or something...
And be on the look-out for Almorexant; it could take a while, but there's little doubt that that will prove efficacious in treating your insomnia.
By the bye, if you're worried about "frying neurons" phenobarbital is not really for you. I mean, it's better that insomnia, but GABAergics antagonize long-term potentiation, the foundation of memory and learning, and that's just as good (bad) as "frying neurons". They also suppress transcription/translation of growth factors since they depress brain activity. Increased brain activity is associated with the opposite, increased expression of growth factors such as BDNF. (Of course, if the brain is too active, you have excitotoxicity.)
