Eh, college is hard and so was his sport. Sure, it's not an exhaustive battery of testing but I'm confident to say he's a normal dude.

Well it's not quite water, it's cerebrospinal fluid and it plays a lot of important roles in waste clearance, immune protection, protection from concussion, and more.

Nope, not related to any disease I've ever seen. The best guess i have is fetal alcohol syndrome but it isn't a perfect match. It's just weird knowing he has a very odd shaped brain. And there's a lot of unknowns surrounding it.

What if he sees another doctor and they mention it to him? Would he be upset I didn't say anything? What if it is linked to some disease and I didn't tell him, and he gets sick?

What if it's hereditary and his kid has it, does it explain the motor delays? The premature birth? The problems they have with him sleeping?

Just a lot of unknowns.

Interesting question. It depends. I linked Ev Fedorenko's Interesting Brain Project at MIT up above, they're doing a deep dive into questions like those.

Broadly speaking, if you're born with these anatomical anomalies, you'll be more or less normal. The article mentions the person in question had an IQ of 70, so that's lower than normal, but not intellectually impaired.

But acquired Brain damage almost always leads to impediments. Strokes and repeated concussions, physical injury, etc.

The brain is "plastic" when you're young, we like to say. That is, it's pliable and can mold into whatever shape it needs to in order to adapt to your environment. That plasticity disappears once you get older. It's how kids can learn language effortlessly - when you're born, you have the most neurons and synapses you'll ever have in your life. You'll keep the same neurons (unless you have a degenerative disorder or kill them with drugs), make new synapses as you learn, but broadly speaking as you grow up you prune synapses that aren't helpful.

This is also why kids can undergo massive resection surgeries (or in the olden days, severing of the corpus callosum) and grow up more or less normal.

intelligence is a very hard thing to quantify. People who are good at math might be terrible at writing plays, both of which are intelligent processes.

Kept finding geodes filled with fresh human blood huh?

Measuring the volume of a skull was once a valid way to determine intellect. We make fun of people who believed that, but IQ is arguably a worse instrument, and certainly no better.

The problem is you can't measure intelligence any more than you can measure charm or beauty. All instruments who claim to do so are doomed to embarrass the people who use them.