One-way Ticket

So, I am still unable to purchase round-trip flights as the return window would be outside the 330 day limit... so I'm going with the one-way! As it turns out now, Perrine (my friend in Alsace) may not be able to take the entire week off to come to Ste Cécile to vacation with me, so I'm meeting her in Strasbourg instead. NOW, the problem is that I could not get a discounted ticket to Strasbourg directly. So, Paris it is!

Chicago, IL, United States (ORD) to Paris, France (CDG) Wed, Sep 09
Total Price:
$351.70

Base
ticket price:
$ 196.65
Trip Protection:
$28.95
Taxes and
fees:
$120.10
Service fees:
$6.00
Total for
ticket:
$351.70

First/Middle Name of
Traveler:
Victoria K
Last/Family Name of
Traveler:
Pike

Ticket Price = $ 196.65 + $120.10 taxes and fees + $6.00
service fee

DEPART
United AirlinesFlight: 0608
Wednesday September 09Depart:
OHare International, Chicago, IL, US (ORD) 10:00amArrive: Ronald Reagan
National, Airport, Washington, DC, US (DCA) 12:41pm
United AirlinesFlight:
0914
Wednesday September 09Depart: Dulles Intl, Washington, DC, US (IAD)
5:29pmArrive: Ch. De Gaulle, Paris, FR (CDG) 6:55am

My one-way flight itinerary! I'd say that $350 is most certainly not bad, as far as a ticket from chicago to Paris, and I'll look into the return trip in a few months. United allows me two suitcases, each weighing-in at only 50lbs, I'll really have to pack smart, and think about sending myself a few things before I leave.
I plan on purchasing a train ticket from the SNCF website to get me from Paris to Strasbourg. I could travel from Gare Est to Strasbourg for 22euro at 10h30 or 12h30. The TGV will get me there in just over 2 hours when Perrine will pick me up from the train station. The question: Is three and a half hours enough time between flight arrival and train departure? Should I leave on the later train... in case the D.C. flight is delayed by more than a couple hours?