Just a quick thought on the FLASH POINT expenditure - my group was thinking of requiring an FP to be spent *before* the roll to modify the dice roll to 3d6, keep the two highest. This would remove the uncertainty of a re-roll, but keep the roll exciting!
The only problem with a "roll 3, keep 2" advantage mechanic here is such a valuable benefit that it breaks the math, especially considering a player only rolls dice a few times per session.
I playtested the new rule that lets you spend a Flash Point to increase your result by +1, and it seems to work.
But if you try the advantage mechanic, let me know how it feels.