What was your OG, FG, and IBUs? I don't think I'd add lactose to it, but it's your beer. Keep in mind though, you are drinking it warm and flat, it will taste different cold and carbonated. I would pull a sample to chill and carb before doing anything.
Also, I don't agree that more lactose will make it sickly sweet, to me even pure lactose isn't sickly sweet. I regularly use ~1 lb / 5 gallons in my sweet stout and that is not sickly sweet either.