To implement window scaling, all you need to do is to use the pygame.SCALED | pygame.FULLSCREEN flag (bitwise ORed) when setting up the display, something like...
pygame.display.set_mode((width, height), pygame.SCALED | pygame.FULLSCREEN),
and your game will run in fullscreen mode.
For custom keybinding you need to check the user's inputted key, and bind it to the action. I might make a tutorial video on it.= on my YouTube channel. Link here (so you can be notified when I release it :D )
You can also check out the 'Defender Remastered' game I made from my itch.io profile to see a custom keybinding feature, and maybe that will give you some ideas :)