If I purchase a game, is there any way for the developer or Itch.io to remove the game from my computer? Do I own the game or is it a "temporary license"? what are the standards for maintaining live service games after a studio shuts down?

If you buy a game, I would recommend you back up the installation files it up on a cloud server - whichever one you use because as itoldyousoso said, they can be removed from Itch.io. If you keep the installation (zip) files, you can reinstall it.  

But even with the backup, the game might stop working after a few years because of updates to Android / Windows etc. So it's not a forever license. There are some games that are regularly updated though - if you click on More information it shows you when the game was published, and when it was last updated. It will give you some idea whether the developer is still supporting the game.