I’m sorry this is happening.  Unfortunately, diet alone does not necessarily indicate if a child will have cavaties.  The latest finds are that there are different types of bacteria that colonize the mouth.  Some are "nice" while others are "aggressive".  It sounds like your child has an aggressive bacteria.  The bacteria can be tested for the type and count.  A high count of an aggressive kind typically means cavaties.  This can run in families as the bacteria is passed on from parents to child.  It sounds like you’ve got a handle on things.  I hope the sealants work.  By the way, my CAH daughter’s teeth are free of cavaties (age 6) and we give her meds at 10pm and 3am while she is asleep.  Also, I have at least 5 friends whose child at an early age have multiple cavaties, teeth pulled, caps etc and they do not have CAH and eat healthy and brush often.   Good luck.  Julia