Feel free to make any content for Attack on Toys: Like video gameplay and monetize, meme, screenshots, and yes you can make maps for it ...but sadly the game doesn't support custom map (maybe in the future? :) )
Yes there is alot of issue report from Linux and Mac version, the game were made with windows and using Unity Build to create Linux and Mac version (but it doesn't seem to work very well based on the report,... so i recommend to play Windows version)
3. Yes that is a bug, should be fixed in 3.0
4. Yes, it is intended... if the Army Men Troop get killed by anything it will turn into zombie :) (Clue to survive the waves: Chinook and alot of chopper + medic)