I'll tackle the question about JHU. Kids have to qualify to take a test called the SCAT. I am not sure if WPPSI scores can be used to qualify, and if so, what score would be needed. But I think an important question is, why? At 4 years old, what are you seeing that would make you think he needs to spend time doing academics on the computer? At that age, even gifted kids need lots of time to play. Play contributes to vital life skills that they will need all throughout their academic career. So unless he is begging to do math workbooks, I am not sure JHU would have much to offer right now, but it might be something to explore in a few years. If you google JHU CTY, you can find out about qualifications.
