Since he’s not a dumb man, and he knows EQ (arguably, they’re always trying to think three steps ahead of each other) I don’t think he’d so easily part with the coin if that would lead Charming to discover he assassinated his father — just because I don’t think Rumple would want the inconvenience of being bothered by Charming clan’s righteous anger.
But if EQ is planning to burn SB to the ground, then Rumple won’t have to worry about Charming coming after him.
Whether or not he’s actually the one who did the killing, I’ve no doubt that Rumple is the one who arranged for Charming’s father to end up dead. Like he said to the Count, he needs Snow and Charming alive and together and procreating. So looking back, Rumple needed Charming’s father to die, so that when the family farm went downhill, the only person there with any way to save it would be Charming making the deal with Rumple to go be a replacement Prince and end up meeting Snow. Who knows how successful that farm could have been if there had been two able bodied men on hand to work it, so dad had to die.