I'm 28 wks, 3 days had a ultrasound done but the baby measuring 30 weeks 1 day what due date due I go by?

Due Date. Your due date shouldn't be changed based upon an ultrasound at 28 weeks. Your baby is just measuring large for 28 weeks.
Depends. If you have a first trimester scan, then go with the due date generated on that scan. You never want to "change" your due date based on a single later term scan.