1) Can't delete items at the moment, as long as it's not for sale just leave it where it is
2) "Game with source" are not designed for people to modify and distribute, they are just for people to have a look at how it was made and poke around. "Templates" would be best by the sounds of it.
3) We can build in custom licensing systems, we've done it for a couple of tools. It does involve some manual work though, but if it's simple "make request to this URL" etc then we're generally OK to add that in to the store
4) Sure!