Just so I am clear on this, Crackshot is the last "modification" made before compare dice, Correct?

For example, I have a ship with an evade token. Tie with crackshot rolls 2 hits. I roll two evades. I must spend the evade token during the modify dice step, then my opponent may decide to use crackshot. If I do not spend the evade token, he surely will. If I do, he will not likely spend it.

Correct?

Technically, it's a cancellation, not a modification, as it happens at the start of the Compare Results step. So, yes, you have to decide whether or not to use that evade token during the Defender Modifies Defense dice step. Once your defense results are set, you go to the Compare results step and he decides if he's going to use Crackshot.

So you are quite correct in your timings.

I agree with Parravon. The FAQ states: When attacking a ship inside your firing arc, at the start of the ‘Compare Results’ step, you may discard this card to cancel 1 of the defender’s evade results.”

Crackshot is performed during the compare results stage, not the dice modification stage. Once your opponent declares their evade results (modifications complete) the dice are compared and crackshot can kick in.