Your mental password-generation scheme is equally susceptible to the “master password” being lost or forgotten. Why do you assume you can remember a bunch of rules plus a password, if you can’t remember the password itself?

Synchronizing is easy, put it in a network share or Dropbox/google drive/iCloud. If for some reason it’s inaccessible, keepass/dropbox will synchronize any local changes the next time you open the manager while you’re at home. This is a solved problem.