Xyrem is not the only treatment.
If I were you I would look into the following peptides:
https://en.m.wikipedia.org/wiki/Delta-sleep-inducing_peptide
And most importantly
https://en.m.wikipedia.org/wiki/Epitalon

As a complementary, I would take glycine 3gramm 5 night per week, which has very low tolerance building and if you watch the studies is extremely potent at increasing sleep efficiency.
I would also consider Agomelatine.
Also I would take potent antioxidants with long half life in order to reduce sleep deprivation toxicity (e.g. ALCAR 2g) and NAC.
Note that alcar can compensate many neuroreceptors downregulations.
Although antioxidants unlike above recommandations are for chronic health and won't likely help your perceived acute sleep.
Finally I would take a potent synaptotrophic in order to reverse large amounts of past neurotoxicity. Taking magnesium l threonate reverse IQ-age by 9.6 years.

BTW is baclofen as effective as GHB? If so then do it as GHB is neurotoxic through paradoxal excitotoxicity, a byproduct of agonizing GHB receptors. Although it's possible that this toxicity can be reduced by taking glutamate antagonists such as memantine

Oh and since you say you have too much REM sleep..
You have to understand that this excess relative to most humans might be needed for you as a way to compensate for other biological deficits, although maybe not.
If you wanna try an original approach, there are drugs that specifically decrease REM, for example IIRC
the benign antidepressant moclobemide reduce REM sleep by 1 hour. Although it improve other patterns of sleep (such as probability to wake up)
https://pubmed.ncbi.nlm.nih.gov/2148341/

Oh and now that I think about it, you mention highly vivid dreams:
Highly vivid dreams can be caused notably by two things:
1) a too high amount of choline.
It is well known (and every lucid dreamer try it) that taking e.g. Huperzine A, which increase choline levels by decreasing its catabolism, induce vivid dreams.
It's possible that your metabolism produce too much choline or catabolise it too slowly.
However be very careful experimenting with choline blockers/catabolisers as choline is necessary for cognition (a nootropic) and is a very important neuroprotectant especially for myelin. Therefore ideally try to measure your choline levels (via urine tests?)
Choline antagonists exists but dose can easily become toxic, as usual everything is poison, nothing is poison, it's the dose imbalance that makes the poison.

The second main cause of vivid dreams is:
Special sleep phases (called ~hypnoagogic) there is one when we enter sleep and one when we exit sleep.
At those transitory levels can be experienced extremely vivid dreams because the brain is in too high wake up state. I have personally experienced 3 times those special dreams while waking up, I was mind blown by the realism of the hallucination.

Note a lower priority atypical sleep promoter is oleamide.

Essentially though I would consider taking eugeroics during the day such as armodafinil or Vyvanse.

Note: everytime you try polypharmacy (combining multiple drugs) titrate doses very slowly, especially the ones that have similar action mechanisms, e.g glycine is a downer like ghb hence slow titration is very important.

BTW I'm sure you did it but diagnose for sleep apnea.