However, I’m never nuanced, I don’t look at all the lines, my theory is weak and I also have a very small dynamic range.
Even simpler than the above excellent advice and suggestions.
Why aren't you looking at "all the lines"? You can, you know. And for extra credit you can and should perform some form of analysis to these "lines." And, simply, learn to sing to them away from the keyboard. And do so. All of the above.
That's an easy one.
I find dynamics to be something you can only learn by (i) hearing (ii) playing. Again, and again, and again.
That just takes some doggedness and maybe a willingness to sound like various other pianists at first.
But learning to hear and understand lines: you have to make a choice to go the slow road for that one, IMHO, because that will take time. Takes me time, and I've been playing since forever. Not that I'm no Eddie Van Halen of the piano, but, you know, I can do some stuff and it still takes me concentrated effort.
It isn't some computer keyboard, the instrument, nor some puzzle like a Rubik's Cube or a chess endgame. You have to do everything to it, and in the process, do everything to your ear, voice, mechanics, and overall sensibility. Even if it means destroying or rebuilding your entire Weltanschauung.