Yes..that stinking kip. It will come. It is as much about timing as it is about strength. I agree with the ones saying leave it in the gym. He will get it.
He seems to have a lot of equipment at home...bar and rings? The pull ups, etc are great for home, paralletes are great for doing strength, and the home mushroom is good. Not sure about rings and bar. THe kids in our gym that have come through and have had all of that at home, have burnt out much faster than those who leavel gym at gym. If he likes fitness, have him do other things...bike rides, skating, playing at the park, etc. It will keep his enthusiasm for the sport much longer!!
Good luck! I am sure we will see that kip soon.