There is nothing you can do about the lag. Arrow key movement is just something that doesnt work well in online maps. Even Azeroth Gran Prix, Blizzard's official map with the most well-done arrow key movement, doesnt work on b-net that great. To make it more multiplayer friendly, you'd probably have to do away with it.
And as far as the backflip animations go, if you have the WC3 file converter from the tools section, you could remove them in literally a minute. I can tell you how if you dont know (I did it when I used those models in one of my maps, because the backflips bugged me).
I'll give this map a try soon.
-VGsatomi