mphrey, I would go with 11 speed. I think cassettes will be easier to find going forward, as are compatible shifters. That 10 speed crank should work perfectly with 11 speed chains.

11-27 with a 36 will be much lower than your current 11-25 with a 39, and less likely to be a problem with a short cage derailleur - so that would be my choice. But 11-29 is not a problem, if you really want some low gears.

That's a nice looking crankset. Please post a picture of the build.