This barrel has the 11 degree 'target crown', means the last 1/2 inch on the end of the barrel is a little thicker than the rest of it.  I want it threaded for a FS week after next, will this cause problems?

It depends on the OA thickness at the end, it should not be a problem.

The end of the barrel is about 3/4".  The threads on AR flash hiders are 1/2".  To thread the barrel, you would need to disassemble the upper, and have the barrel turned down and threaded.

Probably better off just buying a new threaded chrome-lined barrel.

I'm going to add a RRA 6-position to my Model "1", then either have the upper rebarreled, or just replace the upper and use the Model "1" for a .22 conversion.

Hmmm, yeah, sounds like Suburban already has the right idea, I have my 6-pos. RRA waiting, and was pondering a new upper, and a Ciener .22 conversion... thanks for the advice