macOS Mojave dual monitor seperate spaces force dock on one screen
I use 2 external  monitors on my MacBook Pro. The dock jumping around drove me crazy.It is by far my biggest MacOS gripe.  I tried the auto-hiding dock but didn’t like it either.
So today I installed a 3rd party app ubar 4. It seems to work well and so far I’m very pleased. The status bar stays where it supposed to. It is very customizable and I am tuning it to my taste. It does cost $30, but it fixes a problem that Apple should have addressed.

The paradigm is similar in some respects to the menu system the Mac had pre-OS X. TBH I was never a fan of the Dock. I felt it was a step backward,but I got used to it. 
But to-date Ubar  is the best solution I’ve found.