I hardly ever use this (intimidation) card (usually discard it or use it in edge battles) but I played it yesterday and was confused on how it worked.

It says that after a unit is focused to strike, place a focus token on it, so does the token get placed after the unit resolves strikes or before? if before, then does it prevent the unit from striking?

IIRC, you have to put a focus token on your unit in order to have they resolving their attack. With this card in play, after you place the first token (or the first two, if you're focusing a card who's at the Force at the moment), you place an additional one focus token on it.

In this way, you have two (or three) focus token on a unit, and then resolve its attack. Remember that, unless some cards allow you to do differently, you usually remove one focus token from each of your cards when you refresh, so that the "intimidated" unit will have problems in the next round

It is a reaction to the focus to strike, so it goes after. If it were an interrupt, it would go before.

It is a reaction to the focus to strike, so it goes after. If it were an interrupt, it would go before.

This is correct. Note that it is a reaction to focusing to strike, which means that the extra focus token comes after the focus token from striking but before resolving combat icons. Rarely relevant, but can be with Dark Memories.