TGV Avignon gets us into CDG at 1:02pm or 4:03pm. Does everyone recommend the 1pm arrival even though flight is 7:30pm?
In my experience, the trains are either exactly on time, 10 minutes late, about an hour late (if there is a problem on the track), or on strike. I have never flown out of CDG, so I don't know how early you need to be there. Personally, I'd pick the early train - but this is because I know I wouldn't enjoy the extra half-day I gain by taking the later train - I'd be too nervous!
I’m leaning towards staying in the vicinity of Arles. Do I need to be in Avignon night before TGV departure for 9:08am train? I will be dropping off rental car at train station drop location.
If I understand correctly, you are asking about driving to Avignon TGV in the morning from Arles for the 9:08 train? I think driving in the morning should be fine. It's about a 30 min drive -- give yourself plenty of extra time, to be safe.
A rental in the town of Beaucaire is under consideration. It looks like a nice location but I haven’t seen much written about it. I am interested in smaller town recommendations.
Beaucaire is certainly small, and nice, and will have less tourists than Arles or Nimes. There's a chateau/fortress on the hill, and across the river in Taracson (walking distance) is a well preserved chateau (and the legendary tarasque!).