Nope, you can put as many tracks for one maps as you want. What I meant by that line is that if you add more than one alternative track for a map, the routine will load the first suited track it finds, even if all the conditions are met. So for example, let's assume you add two alternative tracks for one map, one with variable 0x40D0 and value 1, the other with variable 0x40D1 and also value 1. Now if both variables hold value 1 upon entering the map, the first track of the two will be loaded.
So if you use one variable but different values like you suggested, it should work completely fine!
Well, sometimes you need to enforce the rules when users are walking a very fine line from being edgy and just being outright disrespectful, which infringes on the PC global rules. That's why I stepped in, just to warn that user to ease off a bit.
It's not really needed though. With Jpan's save block hack you can have 4 KB of RAM space which is saved along with the game. For other things there's a memory allocation function which frees RAM. If you need more RAM, then you're probably packing too much into your hack :P