Of course everyone is different, but a few things were helpful to me. I use a plastic dental guard for bruxism, which keeps my teeth from wearing down more, and helps my jaw feel less sore. I hope your splint thing is helping you.
I've always had RLS, which runs in my family, but it was made MUCH worse by a B12 deficiency, and subsequent anemia. You may know from your Nutrition studies, that B12 deficiency is more common now, even in people who eat B12-rich diets. Generally, people lose the ability to absorb both B12 and iron as they age, but it can also be caused by an auto-immune disorder, or, surprisingly, by long-term antacid use. Also, anemia, and even just borderline low iron can make RLS worse. It could be worth having your Dr. check your levels. I take B12, Folate, and Iron supplements now, and it makes a huge difference. I also take Mirapex, which gives me TOTAL relief from the RLS. Neurontin did not help my RLS, but I had no bad side effects from it, or from the withdrawal.
Are you adapting to the mask now? The right mask, with no leaks, and a little time to get used to it, can make life so much better! I hope things are improving for you.