If I start dating someone before my divorce is final, can it be used against me (in a fault State)?
Dating before divorce can occasionally be used against you, especially if you have children. Whether you're in a 'Fault' State or not, you're best off keeping a low profile and postponing any serious dating until you're formally divorced.
This is as much out of concern for the children as anything else. Your children are almost undoubtedly going to have a difficult time adjusting to the divorce (more difficult than you will), and it's best to minimize the number of changes they will be forced to deal with.