That's very normal regarding the crash trying to join #matrix:matrix.org. You need much higher specs and need to be using Postgres database, MySQL probably won't handle it.
Can you post a sanitized version of your homeserver.yaml so we can take a look at your config?
Also are you running docker or something else?
I didn't have much luck following trash guides unfortunately, as none of the examples quite fit what I was trying to do. Great resource though!