I think it's true about the 1cup=1g carb.

With regards to Splenda - it isn't the sucralose itself that makes you charge 1 carb per packet, it's the fillers that they have to add to make it look like sugar. (This is what I've heard.). There is also a liquid form of Splenda which is 0 carbs, but it is not for retail sale. This liquid Splenda is what Diet Rite is sweetened with though, so the carb count for Diet Rite is 0.