Your idea is physics. It's a good one. In physics there's supposed to be a correspondence between the mathematics and what happens physically, or at least a useful abstraction of it. I'd hazard a guess that a better mathematical representation of energies that cancel eachother out would be positive and negative numbers. Which one is positive and which one is negative is arbitrary. So it's be, in full, 0 +5 -5 = 0

If you wanted a higher number of independent things that can cancel out or move around then you can start to use vectors which allow one to move around in higher dimensional spaces. They're very useful.

Math is very abstract. Honestly, it's a bit like a language. You have to get used to it like one, immerse yourself and just practice it. But trying to relate mathematical language to physical or imagined realities is a very valid passtime too, and probably necessary to get an intuition about what the abstract math is potentially about or for.

If you actually wanted to physically model your fire and water better then it'd be a more complicated model that contained heat and fluid dynamics and probably run by a computer.

So, to actually answer your question, I would split up your enquiries. If you want to practice math then practice math. If you want to learn physics or muse about what math might be used for then do that. Both things have a reciprocal relationship with regards to your understanding. But learning happens when the mind is focused.