It sounds like the 'Use Gamepad' option is on, but that only applies if a joystick/controller is installed on the Game Controllers settings in Control Panel.
You can try copying a DoConfig from another folder into the Pandimonium one and uncheck the 'Use Gamepad' checkbox in the upper left corner of its window. I believe it should work, but I can't guarantee it, since I've only used this method on a few other mods...
Anyways, my best run on this... 1'15"3, "defeated" Pandimonium twice (The extra hover height and extended wait before the invisible shots are the sign), weapon used was Shining Inferno. (Formerly known as the Phoenix Inferno, I'll miss you, EC)
Those friggin' blocks hate me so much, I swear...