Hello,
I re-read this thread with your concerns and this is what I would do:
1. You arrive at CDG from Baltimore, MD at 11:30am. Please factor customs and terminal change. Book a flight to Biarritz via Air France/EasyJet/etc leaving around 2 to 3pm the same day out of CDG. The flight is a little over an hour.
2. Arrive Biarritz and take train/bus to SJPP. This has you arriving in the 5pm range.
3. Pre-book your SJPP lodging on Booking.com or via website for 2 nights. Then you have 1 day in SJPP to adjust, get any credentials you need and just ready yourself for the start of your Camino. There is a hostel albergue that also allows you to stay 2 nights and you can request this as well when you book. They talk about this on their wesbite.
http://www.beilari.info/en/our-hostel Booking.com also has several choices for nights on your date.
I think going into Paris and back out of Paris feels like a bit of overload for you if the Camino is your goal.