I plan to travel from Calais to Reims (stay in R for 2 days), Reims to Paris (stay in P for 5 days), then Paris to Milan (will travel through Italy for another 2 weeks. From the research I've done, it looks like we have to go from Calais to Paris to Reims, just to get to Reims. In the Rick Steve's France book it looks like there is a direct train from close to Calais (Boulogne) to Reims, but I am unable to find an itinerary. Also, should I just buy a 2 country rail pass or stick with point to point tickets? I am normally pretty good at figuring this stuff out, but this one has me spending a lot of time going in circles! Any info will help - thanks!
Here's the key to France's great rail system: Paris is the hub, and you typically have to go in to go out.
In your case it may be possible to find some alternative northern route, on slow trains, with many transfers. That might save you a few euros. Still going through Paris is quickest.
If you want to see this for yourself, try a search at the Bahn web site with "only local transport" checked on each screen where you have the choice.
The only way to answer your question about the rail pass is to price everything out.
Adam is correct about the option of avoiding Paris if you want to take a longer route with more train changes.
As an example, I found two alternatives. The first requires changes in Lille, Marne la Vallee-Chessy, and then Champagne-Ardenne - but these last two are almost suburbs of Paris anyways. The second one requires changes in Lille, Aulnoye Aymeries, St-Quentin, and Laon. Both of these take much longer than the route via Paris, which is on a nice and fast TGV.
I also concur with Adam's point to price everything out to see which option is less expensive. Remember when you are pricing it out that to travel on the TGV with a railpass, you will need to pay an additional three euros per seat in reservation fees. If you are buying a point-to-point ticket, the reservation fee is included in the price.