I'm a little different than most people because I actually enjoy being on the road as much as I like camping. But having said that, your plan is way too much. I just completed a cross-country trip myself in a car. One thing I can tell you is if you plan on driving 500 miles in a day there really is not much time to do much site seeing on those days. I once did two 700 mile days in a row in my motorhome and that was pretty much all day driving.
Sounds like you want to see some sites while you're on the road so here's how I would do this trip. You are in New York so much of the stuff on that side of the Country is stuff you could probably see on shorter trips. Since you want this to be a cross-country trip and you have 30 days to do it, what I would do is spend the first few days just on the road and put the entire east half of the Country behind you. Then plan the same type of three day return when you're done. That gives you 24 days to explore the West.
Also I'm not much into the planning thing. My first RV trip was in a rented motorhome and we had it for 9 days. We started in the middle of California and I didn't know if I wanted to head north to the Pacific Northwest or South. I actually made the final decision as we approached the freeway onramp. We ended up heading South and didn't really plan anything. Went to the Grand Canyon and spent some time in Vegas and then worked our way up the back side of the Sierras. That's how my trips usually go. But I've also known people who can't survive unless they have a schedule and a plan and stick to it every day.