I was in the fighter world in my time in aircraft maintenance. I can tell you things I saw as an outsider, but I wasn't an operator in that space, so I don't know the operational details as an insider would. I'm only able to tell the story I told because I was part of the cargo being transported and commenting on what I saw.
One thing to note: The KC-135 normally has a crew of 3, the pilot, the copilot and the boom operator. The pilots are officers and the boom operator is an enlisted member. This aircraft had 6 onboard. They released the names and ranks of the victims and there are four officers and 2 enlisted among them.
That suggests 2 full crews onboard, which in turn suggests either a long distance flight (which seems less likely to me) or a long duration flight in the refueling area. Neither of those add up to me. I can't imagine a reason to fly a tanker from far away to refuel another tanker. In the second scenario, the one with 2 crews onboard would be the one being refueled because it was staying on station longer.. As you speculated, that would have made it the one in the lower position being refueled.
A thought occurred to me: The concentration level required for the precision formation flying during refueling is intense and probably exhausting. Since they are supporting so many combat aircraft and needing to stay on station for long periods of time, maybe they all have 2 aircrews onboard so they can swap out periodically to rest? Like I said, I never worked in the tanker world, so I don't even know if that is a thing.
Correct, no ejection seats on any cargo or tanker aircraft that I ever saw. I would guess that is because they are frequently transporting people and they wouldn't be able to eject. I would also add that the only parachutes I ever saw were army troops that were going to jump out of a perfectly good airplane.
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