I agree with you DrD about #1 and #2. If you will indulge a little speculation: judging from how the keris is held, I would surmise that the intention was to simply keep the hand from slipping down the blade on a thrust if one's grip slipped. I think it would feel better to put solid pressure on the hand there than at the fingers. It would also make sense that it would protect the users hand when parring an opponents weapon with the blade (assuming this was a strategy with a keris), the decoration acting as a "sword catcher" in the sense that a blade couldn't skip or slide past that area and onto the forearm, but I can't see getting enough leverage out of it to disarm or catch a blade though.

Tom