Since the game is made in PICO-8 I don't have much control over this -- it only supports 2 buttons. Theoretically they could be swapped, but there's not really room in the cart to add more options to the in-game menu.
If your device runs PICO-8 natively you may be able to change the bindings in a config file (see https://pico-8.fandom.com/wiki/Controllers#Configuring_controllers)
There's also an option in the game's pause menu to change the autofire mode so the main fire button doesn't need to be held down, if that helps.