University; there's a difference between the two in Canada.
Why don't you give your buddy some breathing room and let him do his own investigation on his own time? He's only 16. There's plenty of time to develop his interests and talents and that's what's most important. The kid needs freedom to explore. Let him.
he has very strong Si and doesn't ponder or analyze things much.
These seem contradictory. Pi generally means a lot of internal thought and reflection.
doesn't know if he has a rich inner world anymore
This doesn't match with Si either.
He wishes more to gain a general understanding of things to work with rather than a complete comprehension of them. [...]He can be swayed by empirical evidence, skims a lot while reading
Yes, that sounds more Te than Ti.
Yes, it sounds like he could be ISTJ. Si is a rather lovely function when it comes to writing, with its attention to sensory experience and rich detail. Te could be a very useful support function by structuring flow of poetry or plot of prose. Of course he can be a very successful writer, if he enjoys writing and has a natural talent for it. Writing is such a varied and open field that four generalized statements about his preferences mean essentially nothing.
oh yes, because we ALL know that anyone with an S in their type lacks imagination and the ability to come up with shit off the top of their head... there's no way in hell that anyone with an S in their type could EVER be a writer!
Human beings make life so interesting. Do you know that in a universe so full of wonders, they have managed to invent boredom? -Terry Pratchett