Don't grip the bow, let your pulling hand apply the pressure to the space between your hand and your index finger, the bow will actually fall away from your hand upon release. I'm no expert but there are many already on this page.............
Check your brace height......If it is too low,then string could come too far forward and slap you.
Happened to me with recurve,set height and no more slap
it depends - I can't my bow pretty far to the right which pushes my elbow out, which of course moves my forearm just slightly to the right. But yeah that lower brace height (compared to a recurve) can be a factor too.
I was in Cabelas a few days ago and they had a longbow (not a Bear Montanta, just some store brand 68" that is similar to a Samick SLB) and I handled it for a while. Wow I really miss my longbow - I forgot just how light weight and natural they feel.