CanI just correct some misapprehension concerning the use of "Stall".
A forward CG does not cause the aircraft to stall at a higher airspeed. A heavier airframe does, in level flight.
When an airfoil (or aerofoil asI prefer) stalls. this is due to an abrupt separation of the airflow from the surface of the wing. The air no longer conforms to the shape of the airfoil and, typically, becomes turbulent. Because the air is not now deflected downwards, lift is lost and the netremaining lift usually moves its point of effect further aft, causing a downwards pitch. Out of compressibility, the stall depends only on the angle of attack to the airflow. If the aircraft is heavier, then all positive G regimes of flight will need a higher angle of attack than a lighter airframe, meaning the airfoil is closer to the stall.
If the aircraft is nose heavy (has a forward CG) then the elevator will be commanding "UP" for most of the flight, aided somwhat by the propwash. If the airframe has an odd response to throttle, ie it pitches down when throttle is applied, what could happen if you close the throttle on approach is that reduction of power causes a pitch up, followed by loss of airspeed and loss of authority of the elevator that is no longer able to keep the nose up at the reduced speed. The nose drops and speed builds again. At altitude. the speed would build until the nose could be raised again.
This type of swooping is called a phugoid and quite often you will see indoor models do this kind of thing. You were unfortunate that the ground appeared in the middle of your swoop.
My suggestion would be to use the throttle to control the rate of descent on the crosswind leg and on final and use the elevator trim to take the strain off your thumb. Just use the throttle lever a click at a time to bring the model in a constant line of descent to the threshold and just before the end of the runway, at knee height or less, smoothly reduce the throttle while trying, with elevator, to level the model into the 3 point attitude. If you get both things smoothly synchronised, you should plop it down under full control.