Responses
Yeah, but the fact that he was calm enough to plan so much just means he actually just acted on partial information. Sure you want to go back but you got to know more to actually have a chance to succeed unless he has a super OP ability.
What I'm wondering about the most is how does he know that leveling up will mean he can get the ability to return to his own world. Like, is there a book somewhere? Did he hear it from someone else? (which would be shady) Did he just make an assumption?
I can see Tatsuya's reasoning. A bunch of teenagers were summoned there against their will, and expected to put their life on the line for strangers in another world. I'd be royally pissed off as well. You can compare it to being kidnapped, and being forced to fight and kill others in underground fighting rings. No reasonable person would just go "Okay! I'll fight for you!" It's just that his methods are incredibly selfish and evil as all hell.