I've never harvested yeast from a commercial brew myself. But dupont would be great. I imagine they use the same yeast for any of their saisons, but Saison Dupont Vieille Provision is the classic.
As for the recipe it looks great, I'd scale back the Munich myself, I didn't do the math but the colour may approach the upper limit of the style. That only matters for competition though.
You should also consider adding some sugar to help attenuate it down. It's not a necessity, but that seems to be quite common. Up to 20% is acceptable.
I don't know your efficiency or target OG but my recent 6 gallon batch for 1.057 at 68% was:
.75 Wheat malt
2 oz caramunich
1 lbs of sugar
I used goldings and saaz @ 60. And 1 oz of Saaz at 1 minute. about 29 ibus total.
In Process - Russian Imperial Stout, Nelson Sauvin Rye IPA, Mild No.3
In Kegs - Barley Wine, Apfelwein, Wild BlackBerry Wheat, Coffee Oatmeal Porter
Gone - so many :(