KLaFaille

1. If you mean is it possible to stop the gun as soon as you release the trigger, it is not. When the trigger is released the gun automatically fires and clears itself of ammunition as the barrels stop rotating. How many rounds are fired after releasing the trigger depends if the gun rate is set to high or low, there is no way to set a burst quantity. In reality the gun clearing itself might lead to unfired rounds being returned to the magazine and thus becoming unusable, but I don't believe that happens in the game. I could be wrong though. 🤷‍♂️
2. Yes, you need to actively start fuel flow from externals. External tanks are fed from whatever the switch on the fuel panel is set to, either wings or center.
When an external tank is feeding the internal ones, you'll see the fuel quantity on the totalizer increasing. The totalizer only displays internal fuel, there is no means of displaying external fuel. The pumps will transfer some fuel from the external tanks, then shut off for a bit which will illuminate a green advisory light on the caution panel. After a while, they will start transferring fuel again, and the light will extinguish. This is normal and repeats until the selected tanks are empty.
You know your external tanks are empty when the fuel totalizer stops increasing and the green advisory light does not go away. It takes a while, so don't jump the gun and jettision tanks when you first see the totalizer stop and green light illuminate.
https://youtube.com/watch?v=2u2yLEM1iHM&si=9Q1tTyrZAVGc48PU

I was able to roll back to the 12/19/23 version 2.9.2.49629 and ran the 1200, 12,000, and 30,000 foot tests again and got the same results; the traces matched each other almost exactly and well within any sort of margin of error. The only difference I found was that the jet could reach higher speeds in MIL on 2.9.2.49629 than it can now in 2.9.3.51704.
First value is full MIL in previous version 2.9.2.49629, the second is full MIL in current version 2.9.3.51704:
1200 FT: .97 vs .95
12,000 FT: 1.02 vs 1.0
30,000 FT: 1.13 vs 1.08
The results still don't make any logical sense to me, especially in the FPAS curves, where usage abruptly just levels out and starts to decline. Though, as I said, I don't pretend to understand the math or theory that governs fuel usage. I think the other changes in the FM were enough to have me take a closer look at fuel usage, as it seemed different now, which, as it turns out, is not the case.