You can run into a full flt in Jan, and a full one in the summer... less likley in Jan, but when you travel on standby, even as an active employee, be flexible and look at the loads. You're never "confirmed" when flying standby. Once you get your seat, you're pretty much on the flight, and when you change planes, you're back on the list again, waiting to see when you clear. DL does not fly to CDG from LGA. That would be JFK. I'd go PDX/ATL/CDG and dont set yourself up for being stuck in ATL for a week. Again, call the number to check on loads and be flexible. When flying S4, even though it is the lowest priority, what matters is the DOE on the ticket. If the employee who gave you the ticket had say, a hire date of 1969, you're pretty good. Hire date of 2002.... look for a wide open plane. Hope that helps.
PS - on your return... get to the airport early. CDG has a reputation of rudness and cutting off the boarding for non-rev's early