Rabbit,
I load 12ga. 2 3/4 dram loads (75gr. of 2f Goex) and 1 oz. of 7.5 shot. It is a very effective load.
Your wads are very useable. I mainly use blackpowder 2f Goex but I have a friend who loads Pyrodex. I find in 12 ga hulls usually don't burn through but I usually shoot the hull once and toss it. However, your right paper would work better. I pick up plastic field hulls (high brass hulls) at my local trap range,I can always count on bring some home. Look for deer hunters sighting in their slug loads in to, great hulls too. I have 100 loaded and and easy 100 hulls ready to load.
I keep Rem, Win and Fed hulls in separate bags ready for loading. I used to use Win. Super speed but they don't roll crimp very well. Word of Warning-My 10 ga. however eats plastic hulls but I have the Republic Metallic Cartridge load 5 drams (135 gr. approx)and 1 1/8oz of #4 bismuth. that is alot of powder going off. I plan on duplicating the load with Rocky Mountain brass hulls.
As for fold crimp? You would have to play around with your load. I cut my hulls to 2.5" for my 75 grain load and then roll crimp them. I think it would be a pain to push the wads through the crimp. I prefer using 3 or 3.5" hulls and cut them down. This way I also get a perfectly round hull to load. The 2 3/4" inch hulls work but are kind of a pain as part of the crimp is left when I cut them down.
Leading will be a problem. I usually clean out the powder fouling with my garden hose and then use Hopppes or Rig 44.
Check out this website for blackpowder loading. Good info.
http://www.tbullock.com/bpsg Sorry this is long, I hope it answers questions. I really enjoy shooting blackpowde loads. I plan on having my LC Smith out for doves this September. Blackpowder bismuth loads out to really suprise some people!