A crafter doesn't need to use a Fate point to have a potion at hand; she can also do it with a Lore roll. And given that she does have a high Lore, that would rarely be a problem.
True. Since it doesn't specify, I'd guess that the roll would be treated as a declaration, thus having a difficulty between 0 and 6. Well, actually 0 to 4, since the answer to question three is going to be 'yes' for this situation. You'd still have to come up with interesting/funny ways to use the bullets with interesting/funny consequences if you want to keep your failure chances low. Might be fun coming up with such ideas...
Defensive items can be activated without need for an action.
True, which is why I directed my comment at stuff that "take the form of attacks, maneuvers, or skill uses". Which, I think all of your effects do. Including Veil, which is treated as a Stealth substitute, which is an action (as opposed to a defense roll or use of an existing block, which is not).
Triggers can also be put into thaumaturgy effects so they activate on a specific condition. Since any thaumaturgy effect can be built into a potion, the bullets are built as landmines and defensive items, each with its own trigger. The plus is that you can use them with the gun with no extra action. The minus is that you can't use them without their trigger at all.
Of course, landmine effects require
two Thaumaturgical effects: the power you want to discharge, and the ward to hold it at bay. Also, wards are stationary and require a fixed boundary to be set to. So I can't see their use with bullets, and even if you could you'd need two effects per bullet.
As for the veiling, thaumaturgy veils don't automatically break if you attack; enemies simply get another chance to notice you. But with a veil that can be 10 shifts, nobody is going to notice you without The Sight or other magical senses.
Or the several declarations they make, like "Holy crap, I heard an
immensely loud noise coming from right ...
there", along with "And I'm almost positive I saw something flying back five feet or so!" :p
As a suggestion for your veil effect, why not move away from bullets, and instead have an enchanted duster that grants several Veil uses per session? Heck, you could get away with one use, then feed mental stress into it, since you aren't evoking... In fact, you could probably do similar things with the other effects that are less "bullety". Like, for example, enchanted cigars that are activated by your variation on the theme of "Do you feel lucky ... punk?!" which gives you that maneuver. Still well within the western gunslinger motiff.