JOMO, have you considered cutting north at Mobile to Jackson, picking up I20 to Dallas then to Denton, to Amarillo to pick up I40?
As for camping cabins, google them for the area you are interested in staying. There is a lot of info on them.
Good luck to you. Be safe, take your time and enjoy your trip. I applaud your decision to take the trip. Be forewarned, it could be addictive!
Almost all of the Oregon state Parks are worth visiting. You can't really go wrong. Netarts Bay RV is a great private park. If you are a veteran, Oregon has a Veteran's pass which entitles the holder to 10 nights free camping each month. It can be obtained by mail. We used my pass a lot during our 3 months spent in the North West several years ago. Hope to be able to return this year.
The Gunnison area has a lot to see and do. A lot of scenic drives and places to go. Crested Butte is nearby and worth spending a day visiting. There are some nice RV parks in the area. Nice museum to spend some time in. We went there last year and planned on 2 nights, but ended up staying 2 weeks and would have stayed longer if it hadn't been for one of those infernal Dr. appts back home.
I guess a lot of folks don't like the drive on I-10 through west TX, but I always enjoy it. One stop you might consider would be Ft. Davis and Davis Mountains State Park, about 1 hr. south of Kent TX. Nice country and good campgrounds.