One small nitpick if I may... Your interview questions aren't stellar. Better interview questions are behavioral driven IMO, e.g.:
> In our business we sometimes need do [activity]; can you tell me about a time when you [did activity]?
And then probe deeper, as they answer, on the hows, whys, and their decision process.
The same applies to sales or engineers. Or most if not all other knowledge-based jobs, for that matter.
What blogs do _you_ read?
I don't read many blogs, and especially not marketing blogs. I'm subscribed to http://tomtunguz.com/, https://www.kevin-indig.com/, backlinko.com, and https://len.podia.com/inner-circle. Even so, I only look at the post titles in my inbox and click through when it's relevant.
The world of growth/marketing advice is super noisy, so I mostly learn from experience and from trusted friends/mentors/advisors rather than blogs. Then I try to distill that in my own blog.
Being a self-learner I tried my best to find good content for him to learn on his own (Hubspot has amazing lessons for anyone starting from 0).
Today he went on to his first marketing job interview.
What would be your advice to him?
Another thing I have been discussing with him is how he can take advantage his current Organisational/Work/Social Psychology (thats was his specialisation) knowledge while working pursuing a Marketing career.
I think there should be good insights in Marketing once you better understand human behaviour.