Removing cranks?

I can only suggest you get someone to help. With them pushing downwards on the opposite crank while you also push downwards with your allen key on the other side, you should be able to move it easily.

or get a decent length of tubing (like a bit of ski pole, if you have that kinda thing lieing around) pop it over the top of the longer length of allen key, and hey presto more leaverage... if you keep the wheels on and use a wall as a brake it helps to to stop movement (2 points of contact)