I think the sky fly has an issue with the control lines coming loose at the control horns on the elevator, causing a dive to impact. I would make sure all is secure there before continuing and check carefully before each flight. If you do a search you may find some more information on this and maybe some glue suggestions.

Throttle: Many planes will hold altitude at about half throttle and fly much slower there. Climb the plane to a safe altitude and experiment with throttle settings to see how low you can set the throttle without losng altitude. That should be your default throttle setting for a while. Also, if the plane seems too fast for you, that may be a symptom of flying on a field that is too small. If you can find a really big field (600x600 feet), it may not seem so fast.

Turning: In general I think you would be better off avoiding the beginner setting that mixes elevator with rudder. I think you will find the airplane more responsive and less likely to stall in the more advanced mode. Just use very minimal rudder inputs and keep the bank angle low (less than 30 degrees). You may not need to add any elevator in a very shallow turn. In steeper turns, watch for the plane to begin to dive and compensate with up elevator. The higher you fly, the longer you will have to recover from an overbanked situation.

In general, try to use the slightest, most gradual control inputs that you can and give the plane a second or two to respond. This will keep things under control better. And of course avoid wind. Flying in a light 5 mph breeze will be twice as hard as flying in perfectly calm air.