It says (p. 233) that spending a Fate point is a free action, so I assume you can spend multiple points during your turn. But it also says that they can be spent as a reaction. Does that mean you can only spend one when it is not your turn (and only if you haven't already used your reaction)? Or can you take free actions during a reaction? I'm also assuming that you can use Fate points out of combat (like for Aquisition rolls) but that wording isn't as clear as it could be (should haave stopped with "at any time" and left it at that .

My feeling is to let Fate points be spent pretty much as often as, and whenever, players desire - but I also want to know what the rules intend.

I think you are correct. Spending fate points is an entirely meta-game sorta thing, and are thus not really constrained by action rules. You can spend them whenever you want. Even if that is spending one to gain more wounds in-between two attacks against you, or to reroll a parry roll on your opponent's turn. And yes, you can also spend them to re-roll aquisition tests or social actions.

Free action: only on your turn.

Reaction: someone else's turn.

Semantics really, FP can be used/burned at all times, even several on the same turn.