I had exactly the same Css problem you described, total frustration on simple matters.
Then I discovered the HTML 5 Grid. I now use it everywhere for complete control. The only other style rules needed are margins and padding.
Self Driven, Community taught Software Engineer. I tweet about how I'm doing it while providing the resources I've used along the way. Created https://devtorising.com
I had exactly the same Css problem you described, total frustration on simple matters.
Then I discovered the HTML 5 Grid. I now use it everywhere for complete control. The only other style rules needed are margins and padding.
It really is a great resource, I use it a ton now!