Not sure about the half and half. Can you check the package? Splenda is zero points. Spaghetti... what kind? If it is one of those new high fiber pastas or if it is whole wheat, it will be lower points. Were the meatballs homemade or frozen? If frozen, you need to check the package and use your points slider. And be warned, some of those frozen meatballs are VERY HIGH in fat, resulting in high points. If homemade, need to know what kind of meat (what percentage of fat), what other ingredients.
If I was going to give you a flat out points count, I would say 6 points for the spaghetti (if it is a regular one and not a high fiber one) and one to two points each for the meatballs. Any sauce? Probably 1 point for 1/2 cup of regular sauce without meat (unless it has lots of fat or sugar... then it would be more points). And my guess for the half an half would be 1 point for each tablespoon. HTH.........................P