First off, welcome to B&B! Secondly, don't get discouraged and give up just yet. Sounds like you have a good setup and some good products you're using so stick with those, don't make drastic changes. Personally (along with many others) don't care for the Derby blades, for me they tend to be an unpleasant experience (tug, pull). I would recommend a blade sampler pack so you can experience different blades, but above all your prep is the most important component of a quality shave. Try to concentrate on applying very little to no pressure and take the time to map your beard and that will help determine what direction to shave in to get a good shave with minimal irritation. It will take practice and there are times I still tear myself up but when I think back and wonder why it is usually because my prep suffered or I hurried and didn't have the fundamentals in place.
Oh, this Twinkie thing, it ain't over yet. -Tallahassee