Hello,
I don't know if OP has fixed his issue with afterburner, but i encounter the same issue : afterburner won't engage beside the throttle being pushed after the threshold.
I also encounter the issue with fuel (linked ?), playing the Operation Earnest Will Redux campaign. This fuel issue seems to appear randomly, and when it happen, i'm unable to refuel ("nan" being wrote in the refuel/rearm panel) and trying to hook to a supercarrier catapult is crashing DCS.
Dunno what can i provides to help understanding those issues.