Did i break my motor?

How can it run fine and yet have a serious loss of power?

you do Not run opti-2 at 30:1
it has a specific fuel ratio to mix it at and doesent work worth a s#!t if mixing instructions arent followed.
i suspect it immediately plugged the exhaust screen,along with chunks of the foam it injested,not to mention fouling the plug.
best to check the screen in muffler,and if at all possible,get a look in the crankcase to see if some of the foam is in there too.
what i have read is break in is up to 300 miles,depending on a few variables.

good luck.

What's wrong? Well, the motor is not supposed to eat the air filter.... So I would start by pulling the exhaust and intake and probably the head to find out where the filter ended up, then move from there with what you find...

I wouldn't want to leave the filter down in the crank case if it were mine...
The head, jug and piston come off pretty easily and you can probably do that without damaging the gaskets. Perhaps with the piston out you can locate the filter and use some needle nose or something to pull it out?
Depending on how broke in the motor is the case may split easier, or not. I've only split a few, but one was well run and split pretty easy, another was new and was a P I T A...
I would be hoping I could get it cleaned out through the top end one way or another if I were you....

probably just as cheap or nearly as cheap to buy a new motor as it is to rebuild an entire engine. my dad is very experienced with small engines, and he says that the jug, piston, and rings should all be broken in together, that you shouldnt use a broken in piston or rings in a new jug, and that you shouldnt use a broken in jug on a new crankcase. so if you rebuild the bottom end, you might as well just get a new engine. there are much safer performance mods that are much better for your engine than a nos kit. personally i think the air filter went right through the engine, caught on fire, and came out the exhaust still burning, and that could explain the flames coming from the engine.

when the crankshaf is split to replace the big end bearing,it would need to be re-indexed.
the crankcase should be fine.

NOS? At 15mph??? I get great performance all the way up to 30 without NOS. There are many less expensive and less destructive performance mods. Tear it down, make sure it's all okay, put it back together. While you're putting it back together, you could maybe trim the piston skirt on the intake side (look it up) and clean up the ports.

BigButterBean: You can totally mix and match old and new parts, it doesn't matter at all really. Ideally, you'd want to match new cylinder to new rings, but you can put a new top end on an old lower end and it will be perfectly fine. In fact, last time I had to replace the cylinder I just kept the old rings and piston. Worked great, I have lots of power after those broke in together. Since it matters apparently, my dad has been running a snowmobile repair business for the last 30 years.