It says, "After you perform an attack..."

Based on what it says in the latest FAQ p. 1 under the "Rulebook (Page 10), I'm assuming I can use any evade or focus tokens (if applicable) before he can strip them away. Is this correct?

It doesn't happen until the attack is completed. So you would get a chance to use your evade/focus tokens before he strips them.

Rulebook page 10 lists seven combat steps. Wes triggers after the last step. You may use any tokens during the attack. You deal damage. You resolve critical hit cards, if any. After that, Wes triggers.

Thank you!

So basically you are forced to use the evade or focus token (if you can) when he attacks your ship or he strips them anyway when the attack is done.