Mike, I have used a credit card to pry the forearm off in the past. Less chance of damage.
Yes, something non metallic. Even a thin plastic putty knife, or spatula.
Um, no actually. The forends on virtually all modern double shotguns are designed to be pulled off with nothing other than a finger tip and reasonable force.
Some are simple spring loaded pull- off mechanisms and some have other mechanisms such as an Anson, lever, or a pushbutton release, as this H&H apparently has.
None of them are designed to be removed by prying them off with screwdrivers, putty knives, or any other tool. Repeatedly needing tools to assist is applying excessive force, and that may eventually cause further problems. Perhaps expensive problems. What is needed is a correct diagnosis, and then a proper repair or adjustment.
Some stalker should be along shortly with a photo of an antique double that has the forend attached with a pin or wedge, to prove I'm wrong.