I think there are both reasonable and unreasonable expectations for people to care about privacy. Asking that your friend has a different email for everything is unreasonable. Asking that he uses a VPN all the time is also unreasonable.

For every ask, focus on explaining the risks and make good reason-based arguments as to how these risks might be realized. A risk for you may not be seen as a risk for him and your perceived probability of risks happening may not be the same as his.

Encourage individual thought. If his privacy tradeoffs are different than yours in ways that affect your privacy than make an ultimatum for the means in which you communicate and/or reference each other (either privacy-focused or not-at-all).