Now you know you’re turning it the right way, if it’s not releasing the problem is likely to be corrosion between steel pedal axle and alloy crank – the force required to shift it will probably break something.
Boiling water or hot air gun on the crank, then Plus Gas on the pedal hole asap before it cools, leave to soak, repeat every hour. If using boiling water, pour over the crank avoiding the pedal (the heat will conduct down to the end), else you’ll get water where you want to put the Plus Gas.
When using Allen wrench, rather than having the crank pointing up, point it forwards, so that the wrench goes past the crank axle – it reduces the leverage trying to spin the cranks, so it’s easier to hold them still.