I don't see the point to this. All their other products seem to be targeted at replacing less private, non-E2EE services. Mail, calendar, VPN, and a password manager are excellent choices with no major well integrated E2EE solution. This, not so much.
Also, I don't really get why they chose Bitcoin, it's PoW and is much less energy efficient than other alternatives while also not being as private as Monero, nor having things like smart contracts.
If you want the answers to the questions you listed, then it's pretty much covered in the privacy podcast called OptOut. Linked here if u wanted to have a listen.