If you have access to bottles of Saison Dupont, I would harvest the yeast from those. There are tons of threads on the yeast forum on how that's done. The yeast they use will give you a very nice saison, much better and drier than T-58 for my taste. To answer your question, changing the bittering hop within your choices won't alter much. Changing the styrians for any of the others you mentioned would. Any type of wheat will aid in head retention. White wheat malt has a ton of starch-eating enzymes, whereas flaked has none, so using white wheat might lead to a slightly lower FG, although in the amounts used in your recipe, there'd be close to no difference.