How do I make paths a part of my hair mesh?

It is not how the hair is done for the games. It is meshed as low poly since the beginning. Search for game style hair meshing process videos to see how other people do this. Decimating destroys mesh topology, also hair is one of the most difficult things to do for the game, so it will take probably more than one mesh to figure things out. I don't know how to easily reduce poly count in this mesh. You can select loops and delete them, this how meshes suppose to be properly decimated. But it will take tons of time for this mesh. Normally artists create high poly mesh by sculpting it and then retopologize it into low poly model. This type of hair like in your file is used for art scenes. The best way to quickly select and delete edge loops is by using this technique. After you select edge loops click x->dissolve edges. Do this twice for every strand. For example the longest strand in the tail is 2304 polys, by removing edge loops you can easily reduce it to 300 polys and it will look pretty much the same smooth.