firstly, I hope you're okay, and the trip to the ER wasn't too punishing.
secondly, I'm not familiar with the board, so this is only a guess, but maybe the board is WAY too stiff for a beginner. The reason your friend's board was easier to maneuver is because it's been broken in over some time.
You can definitely learn on yours, and although I'd say the board is a smidge too short for you, you should be able to throw it around under your weight.
It isn't too wide in my opinion. Especially with angles at 15/0, however, is your friend's stance (width between bindings) maybe wider than on your board?