Shameless self-promotion:
https://www.pluralsight.com/courses/solving-real-world-problems-sql-server-2016-query-store

CheckDB with repair (any repair) WILL NOT fix these errors, so please don't suggest it.
You probably do have some IO subsystem problems, as that's the main cause of corruption,...

Someone restarted the server and deleted old error logs?
If that was my server, I'd be talking it IT security at this point, as it smells like someone's trying...

All my home machines have names out of Arthurian stories.

Desktop: Myrlin (and  new desktops get the same name)
Server: Old server was Camelot, when I got a new...

You can look in the default trace. It rolls over though, so doesn't go back very far.
Other than that, you need custom monitoring (not CDC, that's for data)

How does an error log get truncated?
Unless you've messed with the default settings, it should contain 6 older logs and the current one, and the recovery pending messages...

Before you restart, what messages are there related to the DB in the error log?
There will be messages in the error log saying why the DB couldn't recover. Always...

You don't really need the explicit transaction. A single statement is its own transaction, and since there's no error handling, there's no real gain from explicitly declaring a transaction.

No, serialisable doesn't force exclusive locks or table-level locks.
The isolation levels mostly change how read queries behave, not data modifications

You get a upd lock, on whatever...