1. Is there a cleaner black powder substitute than 777 that is consistent?
No, I do not believe there is a powder that burns cleaner, with as much power, is as non-corrosive, and cleans up with water.
2. Any reason I shouldn't use "409 with citrus oil" cleanser as a spit patch?
I wouldn't. Oil residue left behind would be a concern for me. Besides a spit patch, dab the patch on your tongue, does fine and you shouldn't have to run a dry patch afterwards.
3. What is the issue with 209 primers and 777 powder?
Some believe that the hotter 209 primer will create a crud ring when used with T7... I believe that also, but I have had the same crud ring with Clearshot when I use a 209 with it. When I use a #11 cap not so much of a ring, if any at all.
4. If a breech plug seizes with 777, whats the best way to loosen it?
What qd2 said, I use the yellow gas line teflon tape, it is thicker than the pink plumbers, normally both are displayed together at Lowe's. I also smear a bit of Knight plug grease on the leading edge of the tape... not problems!