Well done. I am sure you are aware that one good loco will not pull as many cars up a 2 % grade as on flat ground, though more than a 3%. Those great stories of long trains are on flat surfaces.
As far as learning a lot, I have only been doing this for 60 years, and I am amazed but how much I don't know. Each day I seem to learn something I did not know before, in fact I did not even know I did not know it.
Okay, Dave, good for you. Just a quick reminder that your 2% grade will take considerably longer to generate the 3" clearance you'll need typically between the rail tops below whatever passes over them if you have tracks crossing each other. If you intend to have nothing over the tracks, no tunnels or overpassing tracks and roads, then you can simply lay the 2% grade.
If you do have an overpass where one track crosses over another, don't forget that you also need a grade length to yield enough height to get a supporting structure under the upper track and still have clearance to the lower rails.