Congratulations on getting motivated, but of course, as your experience would tell you, be careful and take things slowly.
That said, it looks like you're overtraining, which can actually cause breaking down of your muscles. It's good that you're warming up and cooling down, but I have several comments:
*You shouldn't be doing more than 2 exercises that train the same muscles. Later on you can add more.
*Be careful with Free weights if you dont have someone spotting.
*You're spending almost 2 hours a session at the gym. That sounds a bit long, especially if you're trying to take it slow and avoid injury.
* A whole day spent on your back? That sounds like a bit much especially if you have an injury-prone back.
*If you're looking to gain weight (muscle weight, I'm assuming), you will need to eat more calories than your body uses, and you would want high amounts of protein. You could try a calorie counting program/website (I use
www.fitday.com)
Sorry if I sound too negative, but I just think you're pushing yourself too hard, especially if 1) you haven't worked out in a while (this routine sounds like something you would have to work up to), 2) you're worried about injuring yourself. Does anyone else agree?
Good luck with everything though.