For the Vex sectors, when it comes up again, you'll be able to shoot the remaining 1 in the Well, and the 2 in Nexus, completing both sectors in the same amount of time as if you had done all three in one area one week, and the other section the next time around. Splitting the drones across two sectors did not add any exrra time to how long it will take to complete the Vex sectors.
As for dying and losing the buff, the transponder is active for an entire week. If you die, you just need to kill the Fallen Technician again, and you'll get the buff back.
Yeah I understand the Vex Sector one, I'm prepared to do that once that week comes back around. I know which ones I have to do.
But since I used 2 of the 3 scanners for Braytech sectors this week, I'm not able to kill the Techno Squad Leader to get the buff again. I can kill him obviously, but it'll say active braytech transponder required.