You and I have experienced similar projectories. For a few years in my 70's I was able to sleep well at night but only with the help of marijuana, not a lot but nightly. I knew that inhaling smoke in my lungs couldn't be a good thing, and eventually I began to have serious issues with short term memory which was actually a little scary. I also drank more than I should. So finally I just decided to quit. It seemed like the only option. And it has taken many months to find my new norm, but I think I may have it now.
My sleep now is nothing like in my younger days. I go to sleep later when I truly begin to feel sleepy, and usually I will be slightly fitful until I get up in a couple of hours, go to the bathroom and maybe even sit and read for a bit with a glass of warm milk and honey. That really does the trick though. I may get up once more for another bathroom visit but it seems to work. I don't think I get much more than 5 or 6 good hours now but that seems to be enough. Short term memory has returned and lung capacity seems to have increased. I do exercise 3 or 4 times a week with a trainer and that is absolutely necessary for a whole bunch of reasons.
It was hard to stop cold turkey and it took quite a while, many months, before I started to find the new norm. There were nights I only slept an hour or two, which resulted in naps during the day and another night of sleep problems. I recorded my sleep cycles as instructed by the Mayo sleep specialist, kept the room colder, and all those things. They all helped. I feel like I'm on a new path now, which will be tested as we start to travel more and leave home.
One final note, I no longer smoke marijuana which is great. When I did and tried to use edibles, they just didn't work at all. Now, with my cleaner habits, they are effective. So if I really need to sleep I can take a 10mg bite sized piece, and it works. I know though that if this ever became a routine habit, it would simply escalate so I am trying to stay away from that particular solution.