To me, dark roasts are all about the bloom. I also think 5 pours might be too many, but YMMV. I wouldn’t grind any smaller lest you enjoy lots of fines.
I bloom 20g of dark roast with 35-40ml of boiling water for 90 seconds and then I do 3 100ml pours every 30 seconds. This is my everyday V60 coffee.
Fresh Roasted Coffee makes several tasty decaf and half-caf varieties. There’s a decaf dark Sumatra variety that I’ve made many a late night espresso out of with great results. It comes and goes, though.
I’ve tried several of the lighter decafs since I have a friend who’s all but allergic to caffeine, but he loves coffee; and of those, the Ethiopia is my favorite.
If you don’t mind shelling out, there’s a variety pack with 12 samples of various decafs here