"I roll my attack dice, I use a focus token to modify my roll, now I use a target lock to reroll my dice, and then, I use a focus token to modify my reroll"
Tah dah!!! Perfectly valid!.... Or not?
Not a particularly good idea, but perfectly valid. You don't get anything from spending multiple focus tokens to modify a single roll, even if you put a reroll between them.
As to the larger discussion, Buhallin etc. are completely right. The critical language is this bit:
A ship may spend a cloak token to decloak immediately before revealing its maneuver dial.
As Buhallin says, the latter bit is a trigger with a timing instruction, and the former bit is the effect. It's no different than any other triggered effect in the game, so the right analogy isn't whether you can spend multiple focus or evade tokens to modify a single roll--it's whether Soontir Fel's ability allows you to gain two tokens from a single stress.
There's just one trigger--revealing your dial. That means there's just one opportunity to spend the cloak token, which means you can decloak exactly once per round.
Edited by Vorpal Sword