Hi Jeremy,
Regarding the first question, I'd like confirm how the user set up the account, via POP or Exchange? If he set up the account via POP and check "Remove copy from server after retrieving a message", the copy from the server will be deleted. As I know, when setting up the account via Exchange, Outlook will be full synced from the server.
Regarding the second question, the answer is no. Currently it is not feasible to revert the mailbox back to Tuesday.
Moreover, if you upload his old archive to the account, please set up the account via Exchange, then the emails will be synced back to the server.
Thanks,
Xinyu