My masseuse says my thoracic muscles are weak.
I think the discs are compressed and physical activity will help more than anything.
There's a gym a block away from where I work (and I can go for free). I plan to try out their rowing department.
I'm 35 with two young daughters and am not ready to resign myself to a life of sitting down.
Note that rowing still involves sitting down
In fact that's my main complaint about it: my chosen exercises are bicycling and rowing, which are both done sitting down, and my work involves sitting at a computer (like yours does), plus I also spend a lot of time playing music, also sitting down. I do like to walk; unfortunately weak knees run in my family so running isn't a good option for me.
Strengthening your thoracic muscles is probably a good idea, and losing weight will help your back (and everything else), but I am not sure rowing is the best way to do either of those things. I would definitely check with your doctor and/or a physical therapist just to make sure rowing won't make things worse. If you use good form there shouldn't be much strain on your back: you push off strongly with your legs and then use your arms more than your back to pull the last part of the stroke, but if you don't do that correctly you can definitely get back strain. You should also be sure to do some good hamstring stretches after your workouts, and at other times during the day as well -- most of us desk jockeys have very tight hamstrings from sitting all day, and that can lead to back problems.