The NexSTAR is a great flying trainer once you get use to it's quirks. They do have a tendency to climb, especially above 1/2 throttle and will glide around forever at just above idle. I highly recommend beefing up the landing gear on that NEW fuse you just ordered BEFORE you put everything back together as this seems to be it Achilles heel.
If your CG was correct I suspect a heavy thumb was the reason for the ground loop. Some of these will fly great right out of the box and some require allot of control tweaking to make them fly straight. I had to remove some of that right thrust (using washers) to make ours track right.
Look up some of post by Britbrat about the Nextstar, you name it, he's done it with a Nexstar .. very good info.
He's posted some good stuff about removing the dehidral, landing gear fix, etc.
Good luck