Hello I will help you with your question,
When your son pushed the clutch to the floor the rubber cup on the slave turned inside out and you cannot push all the way down or the master culinder was damaged for the same reason.
Loosen the bleedre screw on the slave and see if you can push the pedal down halfway with your hand. If you can replace the slave.
Let me know what you find you may have to test further
Tell me exactly how you installed the throwout bearing and that may be another avenue that can cause this
The bearing needs to be mounted to the fork then once the trans is installed the lever for the shaft is pressed to snap the bearing into the pressure plate where it pulls on the plate. If the fingers of the shaft are not installed to the bearing but are resting ontop of the ears (the shaft will turn one direction with the lever removed but hits the bearing in the other direction then the trans needs to be pulled back far enough to insert the forks in the bearing ears.
I have seen the shaft get twisted from the braring being installed incorrectly and too much force being used to try to release the clutch so that is a consideration if you have forced the pedal
Glad to help, don't ask how I came by this info!!
Let me know if there is anything else I can do for you