I agree with you on the "one step at a time" approach to fiddling with the load.
Getting the bullets to fit properly is a very good place to start - that's so long as you're getting good ignition, which you say isn't a problem.

That 60gr Blue Dot should give similar energy to about an 8-1/2 dram load.
Is that what you're looking to do?

Black powder is the easiest to ignite.
Pretty much anything will light black powder.
If your primers are setting the Blue Dot off, good for you!

Cheers
Tinker