How can i build a good re-steal range? What are the factors I have to take in account? Is there a difference between middle and late stage and how stacks and icm influence my decisions?

Than you

The first step is to stop thinking about it as a resteal.

Think about that yourself. Let's say BU opens for 2BB and in one situation, you have a stack of 80BB and in another situation you have stack of 8BB. Is that any different?
Or you and BU both have 20BB at the final table of a MTT and in situation 1, everyone else at the table has 50BB while in situation 2, everybody else has 5BB. Does that make a difference?

Besides that, the range of everyone else who still has cards is obviously very important. It matters if BU opens 100% of hands or 10% and if you are in the SB it also matters if BB defends 100% or 10% of his big blinds.

There are loads of factors that need to be weighed up, and they shift in importance during the tournament. Towards the end, stacksize (especially in comparison to other players, because of ICM factors) is especially important.
Something basic that hasn't been mentioned is that you should be considering whether your 3-bet is likely to get called or will more commonly lead to a fold. Obviously if you expect to get called, your hand needs more equity than when you expect to win immediately. That said, in all cases, blockers and equity are important. It's why AK is kind of the ultimate resteal hand. In some peculiar spots, however, it's +EV to 3-bet any two cards, while on other (rare) occasions you might have to fold every hand that is worse than KK. You have to try and work out the most profitable action given the precise situation. Poker is hard.

Check out Splitsuit Sweeney’s chapter in full ring poker on stealing. Should explain a bit

Do you mean this book? https://www.amazon.it/Dynamic-Full-R...ull+ring+poker

Isn’t that a cash game book? Information there doesn’t really apply to tournament poker..

I agree. for that bit I know cash game resteal ranges are pretty larger, plus in a cash game people usually play at least 100x

Yes.