Titan, one thing that I found to help with my first attack of the evening was to have a cup of coffee before it arrived. That would hold off the first one. But, like you, once I hit the bed, the hit arrived in 10-15 minutes. Not even a lousy 45! Prone and sleep always kicked off a hit.
Additionally, I found that when the cycle was winding down, I would still wake at the appointed' time with no hit! Most disturbing. The pattern took weeks to stop. I would just take a bathroom trip and go back to sleep.
As for the Prednisone, it works for me until I go below 30mg/day. Three 10mg pills and I was golden. Two and I was not! That still holds to this day and it has been decades. Since you took the initiative to stop the injections except in desperate need, it seems like the cycle is winding down? Am I correct there?
Training your brain to not wake at those CH dictated times might be helped by the use of Melatonin and Benadryl. As in take the Melatonin at bedtime. Not sure what your 'dose' is, but up to 25mg is considered safe. I took 30mg many nights before I learned that, so not sure why the limit, but feel that you should know. Anyway, take that 30 -45 minutes before bed. Then, when you wake later in the night, say after 4 hours, take Benadryl then for the sleepiness factor and the anti-allergy benefit. That helps me ditch the 4 wake up calls every night post cycle. In about a month I am free of those wake-ups.
Your doctor gave you an injection of Dexamethasone, not a course of Pred, which is the norm for a Clusterhead. That would not have the same effect of Pred in pill form and taken over several days. So, just drop that med from consideration. A dose pack of Pred - taken for about 5-6 days in decreasing dosage each day may help a lot. Or a course of Pred over 2-3 weeks that has a taper at the end. You taper, not just stop this medication. I am pretty confident that you will be CH free in a day with Pred. But it is a double edged sword and always remember that! You use it judiciously and perhaps a dose pack 2-3 times a year and a long taper say twice a year. You want to avoid the necrosis it can cause and have your hips replaced from it.
As for the D3 Regimen, year round is best. That way your body is prepared if your head decides 'Oh, lets have a cycle in January this year!'. Which it can do!! It is healthy and good for you. Additionally, I have seen some members who only take it a month before and during their cycle, forget to start it and the cycle now comes. Not good!!
Hope this helps a bit.