Quote: "The check button saves it, and the blue save button saves the whole thing as a single image."
So you're saving your levels as image files? Given that you're building your levels based on small ~tiles anyway, wouldn't it be much better and less memory-intensive to simply save inidividual image positions into a file? But on the other hand, if the way you implemented it works well, there is no reason to change it I guess.
About the "run"-button: In Doyle 2 I solved it in a way that my game's exe had an option to run levels using the command line. So pressing F5 in the editor resulted in the current level being saved and the path of the level file being forwarded to the game's exe, which then loaded it and allowed the player to play it, skipping the game's intro sequence, main menu etc.
Pretty simple to program and increases the productivity quite a bit.