No. This is for the same reason that you can’t just cast Ancestral Vision from your hand for free: It doesn’t have a mana cost. This means that when you try to cast it, when the game gets to the part where it needs to know that cost (or the flashback cost, which Snapcaster Mage makes from the mana cost), it gets an error and you can’t proceed [CR 117.6].

Note: Things like cascade, Fist of Suns, and indeed, suspend itself get around the whole “no mana cost” problem by specifying that you pay an alternate cost for the spell. Casting the spell with an alternate cost means the game never has to check the mana cost, so it never finds out that there’s nothing there [CR 117.6a].

No. This isn’t immediately obvious intuitively, even after looking at the reminder text. We have to go to the CR definition of suspend: “Suspend N—[cost]” means “If you could begin to cast this card by putting it onto the stack from your hand, you may pay [cost] and exile it with N time counters on it. This action doesn’t use the stack,” [CR 702.61a]. It isn’t legal for Amy to cast Ancestral Vision from her hand at this point because she’s already cast a spell this turn. Therefore, she can’t suspend it either.

Note: This goes both ways, too. A Vedalken Orrery will let you suspend Ancestral Vision at instant speed. This interaction was well-known during the standard season when suspend debuted, since a popular deck could use Teferi to suspend Aeon Chronicler at end of turn.

No. Generally speaking, once a triggered ability is on the stack, it will resolve, even if the game state changes in a way such that the thing that made it trigger is no longer true [CR 603.3]. Sword of the Meek doesn’t check the creature’s p/t again when it resolves, so the fact that the power is now different makes no difference.

Note: The card Sigil Captain has a similarly worded trigger with a different answer. The intervening if clause in Sigil Captain’s trigger means that the if condition is checked both when the trigger goes on the stack and when it resolves, and that the check must be passed both times to get the effect [CR 603.4]. Jace’s Scrutiny would stop that trigger from giving +1/+1 counters.
Note: The thopter/sword combo can be stopped by a trick like this, but it needs to be a different card. For example, Dampening Pulse will do the trick because its continuous effect applies as soon as the token enters the battlefield [CR 611.3c]. The game will see the Thopter enter as a 0/1 and Sword of the Meek won’t trigger at all.