Regarding n° 2, I think it will never be fixed, given the nature of the service itself, in which all emails are stored encrypted, and the encryption keys are in the server.
But not from an alias: something+johnny@example.pro, other+spoon@example.pro, another+kettle@example.pro.
Addresses are limited in number, 5 on my plan. Aliases are unlimited.
For the second, they've already implemented a feature on their web client to download emails locally so you can search in the body of the messages.
See: https://proton.me/support/search-message-content#the-index-o...