Hi,
I tend to smoke for about 6 hours, but I like my ribs a little more chewy than falling off of the bone. As for rubs and marinades, I tend to go simple with salt, pepper, brown sugar. Or marinate in beer and sauce the last hour. I set the smoker at 235.
Your method looks and sounds good to me. THe main thing is that you like the results and that it is repeatable.
Hardpan