The general consensus here I would imagine is that yes, it is worth it. I've no experience with tourney coaches but I know any coaching I have gotten for cash games have had a direct impact on my win rate, and similarly anyone I have coached has reported an increase in their winrates which they attribute to what they have learned from the session so over time it is something that pays for itself.

Yes of course as long as he finds the correct coach and someone who has been beating the same/higher games he currently is over a large sample. I feel tournaments are pretty much solved but there will be some certain areas he is missing out on.

So yes I would suggest he books say 3 * 1 hour slots as a bit of a tester and to see how it goes!

It varies person to person but coaching can be considered one of the best forms of poker education available. The main reason is that strategy videos and articles or database analysis can't really provide you with the external feedback. That being said coaching can also be pricey so it's important not to invest too much of your bankroll into it. As long as you pick someone with reasonable rates coaching can really help you get to the next level.