> Only really important passwords are in my head.
That has not worked well for me. I have lost a small amount of bitcoin, and some encrypted homedirs and encrypted hard drives.
Yes, occasionally sites don't allow it, but I've found if you use at least one of: uppercase, lowercase, numbers and symbols, and have a length of around 10, then it will go through virtually all sites.
I keep meaning to collate idiotic password rules so you can see for sure which patterns work in all of them, but I've never got around to it.
Some need Lower-/Uppercase, some with numbers, some with special Chars, some restrict to minimum of x chars, some use a maximum.
Your system works not for all things, i use a similar system, but store a bunch of passwords with last pass. Only really important passwords are in my head.