OK.....all's well in engine land. It's kind of rare to see dirt make it's way past the throttle valve, even rarer to see it travel deep inside the crankcase.

NOW, get some contrast on the top side of that wing so you can tell rightsideup from upside down in the blink of an eye.
I like to leave the bottom side of the plane as plain as possible and put all the "art work" on top. When I see a flash of brilliance from the top side, then I've "got it"....just like that.

Sounds like you're making good progress in your quest to get into RC combat, nice going.

I'd get a remote needle valve mounted to a piece of nylon or delrin, stick it behind the engine somewhere and forget about the stock OS backplate set up. If you do this, you'll have a "life-time" set up that almost completely eliminates one more thing that can go wrong.

MECCOA sells a universal NVA, so does JETT Engineering. The best of the best would be to use a OS C/L venturi [ditch the carb] and go with a servo driven fuel line pinch for your engine kill.
The fuel line pinch is mounted behind the engine and the C/L venturi is so compact they almost never break in a crash.