This definitely didnt feel like a 2/5

This one was pretty clear cut for me. The stimulus says in ALL other significant respects. Even if there were 100 other significant respects, missing even one would make them not preferable to semiconductors. So even breaking ONE of those rules (not matching max current capacity) disqualifies the vacuum tubes entirely.

Was it a faulty assumption to assume that

decreased cost of living → more people living downtown → more traffic congestion → /profit increase

That seemed like a fair enough assumption to me.

I guess the entire last sentence is nothing but a trap.