Our trip begins in 185 days. I have not booked our on-site resort yet. If I booked tonight, could I do my ADR's now or do I still have to wait until 180 days?
You have to wait for 180 days from your check-in date.
Plus 10 means you can make reservations on that day for up to 10 days AFTER that. Not that you can make reservations in advance of the 180 day mark for your first day.
Yes, you'll have to wait until 180 days out. Unless you have a resort reservation you will have to do your adr's one day at a time. If you have a resort reservation you can do the 180 + 10.