With regards to multitouch, you will need to modify the source so it uses Input.touches. I did get a contrib a while back with this change, but I haven't got around to merging it. I will try to merge this in for the next release, but I cannot promise it as I am totally occupied completing the tilemap editor right now.
In the latest version, you can hook up to the ButtonDownEvent - this will trigger every time the button is pressed down (rather than released). You will need to do this from script, but this will be much more efficient like this anyway.