Not sure if you will see this at this point, but I have a bunch of sleep issues and the things that I have found that help me stay asleep are: exercise or some sustatined physical activity (you are already doing this), magnesium (500mg any form, however if makes me sleepy the next day even though I slept more), baclofen, and phenibut.

Baclofen and phenibut are similar GABA-B receptor agonists (phenibut also has a weak gabapentin effect), phenibut is more effective at usual doses (600-900 mg phenibut vs. 10mg baclofen), however the side effects are potentially worse in some ways (some people find it quite addictive and heavy use over a long period of time might cause retinal taurine depletion leading to permanant vision loss). However, baclofen has an increased chance of causing seizures, although I think the chance of this is low at 10mg (but phenibut can be started in higher doses while baclofen would need to be stepped up and down). Both have a chance of causing central apnea (as do a number of other medications). Some people don't find one or both helpful (I seem to have a fairly slow drug metabolism that might increase the effectiveness) and even if they do help they become much less effective if taken every day. I've tried various schedules and with baclofen 10mg every other day or possibly two days on and one day off seems to work the best. I've also done 10mg baclofen, 600mg phenibut, and a day off, although due to the issues with phenibut I would recommend just using baclofen. Balofen is prescription only and not commonly used for sleep (even sleep doctors might not know it can help), however there are a few studies using a daily higher dose that found it helped and that was enough for my doctor. I haven't seen any studies using the 10mg every other day. I did try 10mg every day for a month once and it still seemed to do something but it seemed quite a bit less effective. Overall, while not a great option in a lot of ways it has been helpful for me.

I'd recommend against seroquel, valproate, benzos or similar GABA-A receptor agonists, or any of the other more powerful antidepressants or antipsychotics. Some people find them helpful, but others have bad reactions that cause lasting damage. First-generation antihistamines might be better as a "get to sleep soon" drug, either diphenhydramine or, I've heard but haven't tried yet, ultra low dose doxepin (.5 to 4mg liquid form, works just as an antihistamine at that dose but has a longer half-life). Or a few other first-generation antihistamines that are harder to find these days that I haven't tried. However I don't think antihistamines are all that good for sleep maintenance issues.

Some people find delayed release melatonin helpful, however any form of melatonin just causes me to wake up early (this is not all that common so worth trying first if you haven't).

Ok, one other thing: I take 150mg sublingual uridine monophosphate mostly for circadian reasons but it does seem to make it a bit easier to cope with less sleep. The two possible side effects that I've heard of with uridine are digestive issues or there is concern that it might increase the chance or growth of cancer, although I think that seems unlikely to be the case at that dose and hasn't been reported in humans at any dose. I take at least a couple of days off every month or it looses effectiveness.

Actually a few more (that you might be doing already): keep the room as dark as possible when you sleep, ideally block all light. I also found an air purfier to be helpful due to the noise of the fan blocking irregular sounds. To limit circadian issues, try to get out of bed at the same time every day if possible (eventually it isn't if you don't get enough sleep).

I also have the "no rebound sleep" thing most of the time, although it has at least partly come back at times for a little while. I wonder if the loss of rebound sleep correlates with worse outcomes (I am also unable to work).