Sounds kinda like a broken penis, or something close to that. He shoul dprobably go see a doctor. Better safe than sorry, especially if is affecting erectile quality.
Oh yeah, regarding your other questions:
Tell him that what you describe is the most common way that penises are broken (it is). Tell him not to be shy, and that he will regret it in the long run if he doesn't see a doctor. I frankly can't understand why he wouldn't want to get it checked out, especially if his erections aren't working properly. Maybe he's shy? It's still not worth it.