This article does not answer either of these fundamental questions.
2. If my use-case requires me to give someone access to my data in order to do their job (eg a hospital needs to see my medical records), then I think it's mathematically impossible to defend against what you said. (barring unlikely advances in homomorphic encryption and the like). Using public-key crypto allows us to eliminate having a intermediary party and the risk that the intermediary party gets hacked. Blockchain then allows us to credibly prove that our data existed at a certain point in time. Also there are use-cases where I maybe need not disclose all my data (eg maybe for some use-case my bank does not need to have access to my payslip, just a proof signed by my employer that it exists)
The "use case" here is people's lives. People's lives are messy. Blockchain doesn't solve that mess, it pretty much just makes it worse.
We should focus on using blockchain to solve "neater" problems like who owns what and who is contractually obligated to do what, etc. Those problems don't have edge cases that involve a parent who loses their memory or a kid who gets thrown out of his house.