No
Read the sentence in context -
When you cast the spell-and as a bonus action on each of your turns thereafter-you can expend one or two of the meteors, sending them streaking toward a point or points you choose within 120 feet of you. Once a meteor reaches its destination or impacts against a solid surface, the meteor explodes.
Unless and until you "expend one or two of the meteors" they are not subject to the subsequent sentence. The meaning of this sentence is if it hits its target or misses and would therefore strike a solid surface, it explodes; if it misses and would not strike a solid surface it doesn't explode.
The spell does exactly what it says it does, and no more
Choose one object weighing 1 to 5 pounds within range that isn't being worn or carried.
This means that you can't use it on an item that you are carrying, so you can't use this spell on the crossbow bolt hidden in your sleeve. You probably can't cast it on a crossbow bolt anyway, since it most likely weighs less than a pound. However, you can get around this limitation by casting it on nearby objects, like rocks, or by dropping the item you want to catapult first.
Additionally, you don't get any critical or sneak attack damage because this spell requires a saving throw, not an attack roll. This question explains why there are no critical hits on spells that require saving throws. Similarly, the Assassin's Assassinate feature only applies to attack rolls. Thus, you only get the 3d8 damage from the text of the spell.
Finally, it's reasonable for your DM to rule that sharp items could deal piercing damage, but that would be a houserule. Officially, every item flung by Catapult deals bludgeoning damage--if that's what your DM has decided, he is supported by the rules.
Whistling is probably not an appropriate somatic gesture
PHB 203 states,
Spellcasting gestures might include a forceful gesticulation or an intricate set of gestures. If a spell requires a somatic component, the caster must have free use of at least one hand to perform these gestures.
Which suggests that spells that require somatic component require hand motions. Whistling is arguably a verbal component, rather than somatic.
Best Answer
Generally speaking, spells only do what they say they do. The minute meteors only do two things: orbit you, and streak off to explode somewhere via the initial launch or a bonus action. There's no mention made of being able to physically manipulate the meteors the way there is for, say, Otiluke's freezing sphere, and certainly the spell doesn't imply they're physical objects by talking about opposing combatants swatting them out of their orbits or anything. From a strict standpoint, the spell doesn't say you can, so you can't use a minute meteor as ammo for a catapult spell.
A DM might decide to allow it, but they'd be responsible for answering all the detailed questions about how it works in that scenario. For one thing, the spell doesn't say the meteors explode except through the use of the 'streak to a location' effect, so there's no particular reason to think that a meteor launched by catapult would explode on impact. But it's not clear what would happen if it didn't explode (does it come back and continue to orbit?) so again, that'd be up to the DM to decide.
Personally, I think that's a clever combo and would probably allow it to work as you intend -- it's really not significantly different from catapulting a rock and using the usual meteor attack, just costs one less bonus action -- but that's because I like to reward clever thinking rather than because the rules say it should work that way.