Your grain bill is fine. Don't change that at all. You'll get a nice, pale color, with plenty of fermentables with that. Mash temp of 154 is, IMO, perfect.
I'd like to see you double your bittering hops. I think you won't get the hop profile you are looking for with just a half ounce of Centennial. You've got plenty for aroma, though you might consider dry hopping with some Cascade to accentuate that, or move that 1 minute addition to a dry hop.
On the whole, though, this looks like a very tasty recipe, without any changes.
As for a starter, yes, you should do one. As a rule of thumb, when using liquid yeasts, you are always better off with a starter: (1) you don't know how the yeast was handled before you got it; (2) it increases the amount of yeast you pitch, therefore reducing lag times and giving you a more complete fermentation.