There is almost always food available for Shabbos meals. Shabbos is almost always “in” since there is Seder on Shabbos afternoon. However, if he has friends or relatives that live within walking distance, he could go to them for a meal.
The best way to describe the knapsack restriction is that there is a dress code in Rav Tzvi Kaplan’s yeshiva. Talk to anyone who attended any of the Brisk Yeshivas, and they can describe the dress code completely. It is unfortunate that “very hard on his boys” got associated with “no knapsacks” in this thread. Girls have a dress code, why shouldn’t boys?
A better way of describing “very hard on his boys” would be no cell phones in the Bais Medrash. That basically means you will not be able to call him. He will need to call you because his phone will be in his apartment – not in his pocket.
There are rumors that admittance into Israel will be restricted to those who have been vaccinated, so you might want to think about finding a place for him to learn until he gets vaccinated. These rumors are based on the agreement Israel made with Greece that required vaccination.
B’Hatzlacha!