As many others have said-forget the stix !
Check out what the Dr. has to say about them. You get get a negative reading and still be in ketosis.
As for the late night snacking ...NOTHING WRONG WITH THAT.
Your metabolism is what you are going by on this diet, and eating before you go to bed is not a bad thing but a good thing. Also eating when you wake up is the most important thing - why- it gets your metabolism going. Same thing with eating before you go to bed it keeps your metabolism going.
I seriously doubt that it was the Jello, and very few people respond poorly to the nutrasweet, I know several folks that have been on Atkins for years and never had a problem with nutrasweet. Dr. Atkins has no definitive evidence that nutrasweet is any worse than anything else.
Most important thing at this early stage is you are counting carbs accurately. If you have been in ketosis you did it !! I need to keep up with fitday in order to keep them low.
Chin up, you are probably still in ketosis and if not stick with what got you there and keep it up !!