I wouldn't use anything to block cortisol. Besides, there's more to the HPA axis then the cortisol pathway, and besides, GH shouldn't elevate cortisol that much. It lovers cortisol binding globulin somewhat, elevating free cortisol, however that shouldn't have such a big impact on sleep.
There are a lot of other factors involved in sleep and the hpa axis. Vasopressin, neurotransmitters like serotonin, dopamine, glutamate, electrolyte ballance plays a big role too, etc. What you're describing sounds like a loss of sleep pressure and a compression of sleep cycle's.
Either way, I'd stop using gh, as it's obvious you aren't responding to it favourably and such offenses can take time to resolve for some people or even be semi permanent for others, for whatever reason.
I would stay clear of GHRP's. They are the biggest offenders in regards to HPA modulation. Ipamorelin has the lowest effect but stil noticeable. I experienced the exact same sleep pattern on it as you on are on gh. Same goes for mod grf.