HI Queen! Hope all is well.
I got the DVD set and have used it. (Cost me $80 or so IIRC.) I'm not particularly in good shape so I do get a good sweat going with it. I've also managed to lose some weight with it. My own back pain is relieved when I do it regularly.
I suppose you've seen the ad for it. Dallas Page is a pro wrestler and promoter, and his "schtick" during the workout kind of gets old after awhile. The exercises are good, but I don't believe for one second that his "models" got bulked up only by doing his exercises!
I have recommended it to 3-4 people on Arfcom as an easy way to get people into exercising in their homes. I suspect that he's selected several yoga positions which are hard to do wrong, as yoga CAN be harmful if done incorrectly. Also, in the DVD workouts, he has three "levels" at which you can work; for example, the "plank" may be done on hands and toes, or in the "modified" (i.e. "easy") position, on hands and knees.
If you haven't seen his "star pupil," go to Youtube and search for Arthur's incredible transformation.
Short version and
Long version Arthur was a 300-pound man who'd ruined his knees in the Army, who the docs told he would never walk again without crutches. Page worked with Arthur, and now Arthur is doing some of the most strenuous yoga routines possible. YMMV of course.
I think that if you can stick with it, it will be worthwhile to you.
eta
I've justlooked up "spondylitis," as I've never heard of it. I'd check with your doc to see if he thinks it's OK.