Amtrak rail pass

This July a few friends and I are planning on taking the Amtrak across the country and back with bikes (DC->Seattle). You get 10 rides over the course of 30 days, and we plan on going north to Chicago and west through the northernmost states. We’d like to bike from one stop to the other several times along the route. We are somewhat inexperienced and would likely only set goals of 50-80 miles a day along light gravel routes. If anyone knows of good routes that connect stops on the Amtrak along that please let me know. Also any train/backpacking knowledge is greatly appreciated. Really excited about this trip but don’t really even know how to start planning. Thank you!