The amount of weight the child is to use should be limited and not over done. Supervision is of the utmost important and supervision by individual that is well versed in strength training, particularly with youth. I would not recommend maximum weight pressing for preadolescent children, and many weight-training programs for children are currently in use and have been reviewed with very good results. The disk itself is a relatively dynamic structure and a mild bulge may benefit from a good physical therapy program. However, still gaining the benefits of putting the joints through full range in motion without the added stress.
Swimming is also very good from a cardiovascular standpoint.
It is great. A warm up should allow rotation of the torso. Steroids can in fact, lead to complicated heart conditions, liver conditions, kidney conditions and can put the user at high risk for severe infections. Steroids can weaken the immune system to a point where the user becomes at risk for severe infections that can damage a number of their organ systems. I have seen teenage to young adults with steroid use, only to have them end up with severe heart damage, secondary to a heart muscle infection, secondary to the use of steroids.