Our flight plan was just changed by the airline and now we are flying out of Paris via Orly. I had everything planned for a CDG exit so now I need to make adjustments. I checked the SNCF and RER and see that there is no good direct connection like there is for CDG. This is in September and we will be staying in the 7th near the Duroc and Vaneau Metro stations. What is the best way to get to Orly by 6:30am? Thanks in advance!
Enjoy your time in Paris. I flew out of Orly early morning also and had no problems. I ordered a driver and car to ensure I was there on time. From my perspective the cost was worth the piece of mind. The driver was early and I arrived ahead of schedule with time to relax.
Though you could take the Metro and then the Orly Bus, I would either arrange for a cab or uber to make it stress free. Flat fee from left bank to Orly is €30.
If there are two of you a taxi is by far the best way to get to Orly; if there are 3 or more, it is cheaper as well as more convenient than the fiddly complicated and annoying public transport. As you note, there is no simple one shot train from Paris as there is with CDG. It is only 30 euro for door to door service by taxi but you should order the taxi the night before and this adds 7 Euro.
If you don't have much luggage, take the RER B to Denfert-Rochereau.
The Orly bus is right outside. Buy tickets in the machines under the bus stop.
But if your airline requires check in from 3 to 4 hours ahead of departure, I'd recommend staying in an airport hotel overnight.
We took taxi in similar situation