why does symbol sprayer spray so large?

Good question, the symbolism diameter (20 in my screenshot) deceivingly is actually the size of your spray nozzle, not your symbol. My guess is you are asking about the size of the actual symbols, as everyone runs into this confusion. So if you use the left and right bracket keyboard shortcuts to make the brush smaller and bigger that is only changing the size of you nozzle, yes deceiving again.

I would drag out a copy of the symbol, break link to symbol, scale smaller (e.g.: 25%), then drag back as a new symbol. Deceivingly again the 2 symbols in my symbol palette below look the same, but as you can see the 2nd one sprays much smaller for the selected symbol instance on the right.

You can also hold down option and brush over the symbols with the symbol sizer tool selected to make them smaller. Without option they will get bigger.

The symbol tool is a very deceiving tool, that could be written better in my opinion. But we have rcraighead​ on these forums who is a master at this tool and he may be able to offer some better insight as I rarely get to use this.

I struggle with getting the symbol to not have gaps in between them, would love to hear what suggestions others have for that. For some reason my bigger lips are closer to each other, but the smaller ones have more open spaces.