Daniel, My budget when I travel is much less than that. I do mostly hostels, tent camping, campground cabins, or cheap motels. With two of you, it is very doable. Often the cost for two is the same as the cost for one.
You will find purchasing food in the local supermarkets, and making use of cooking facilities in campgrounds and hostels will save you a lot. Most cheap motels have at least a microwave available, if not in the rooms, then usually at or near reception. At many service stations and fuel stops one can find magazines which have discount coupons for accommodation. These are worth looking out for.
When travelling from Yellowstone to Denver, make sure that you go through the Big Horn Mountains - an incredible place, and well worth reading up on and seeing.
With all the National Parks you plan to visit, you will save if you purchase a National Parks Pass. They are incredible value.
And as for your English. You should be proud of it. Much better than most folks I know.
Have a great trip.
Lifey who travels on a very tight budget