Assuming you are making 5 gallons, that is a big malt bill for a Belgian Pale, but only if sticking to the style guidelines is important to you! If not, keep calm and brew on.
I don't think that the maltster of your pilsner malt is going to make that much of a difference, so whatever pilsner malt your store has will do just fine.
Abbey malt is just another kind of toasted malt; some contribute a bready flavor, others are more like a honey malt. Depends on the maltster. Is it appropriate for the style? Absolutely. If your store doesn't have any abbey malt, simply substitute aromatic or biscuit malt. You could even use Victory malt if you wanted to.
Willamette hops should work just fine. And like Joe Sr just said, Styrian Goldings works too.
I would stick with the WLP550, and here's why: it is appropriate to style, is reliable, and this is only your second batch of belgian pale. You know that yeast can have a huge effect on the flavor of the beer, and if you are constantly changing malts and yeasts from recipe to recipe, you'll have a hard time figuring out exactly what works best for you. From my own experience, yeast is the last thing I change when I'm trying to get a recipe "just right."