Hi Op,
This is a great plane to get back into the hobby with. Yes, NP will not give the best tech service as you have found out, but that's part of the cost of doing business with them (ie the low cost of the plane). I've had a bunch of these (have one currently in use as a club trainer), in addition to the Sky Surfer, Bixler, and other Easy Star clones. I've never encountered the problem you are noting. It sounds like a balance issue, and forgive me for saying, perhaps reversed elevator control? I know you have prior experience, so just double checking on that. For the plane go nose in so quickly it's one of those two things I think. The motor already comes mounted and is balanced (to some degree) at the factory. I have never received one with the prop on though, that might be something new. I know you said thrust is coming back from the prop, but you might want to double check...switch it around just for ****es and giggles, you never know.

All of these types of planes should actually float/coast right out of your hand with a little push (balanced properly, and no motor on). Perhaps you have an area with tall grass you can try that in?

As another member mentioned, there is downthrust on the motor preset from the factory. About the worst thing I can say for this and similar planes is a habit of diving (slightly) when full throttle is applied suddenly. If I'm doing tricks near the ground (like touch and gos etc), I always plan a little up elevator right before punching the throttle. I don't know if any other way to counter that. Is there anyone else where you fly that could launch for you?

As you have already seen, a nice benefit of this plane is the ability to repair. Gotta love CA and kicker, or other types of quick set glue.