A few things, based on my own personal experiences..
1) The scan report you first posted is typical of someone who performs a heavy manual labour job. Most people in such situations are a ticking time bomb for a lower back injury, they just don't know it yet.
2) Workers Comp is fucked. Unless you hurt yourself at work with a shit load of witnesses and the injury is blatantly obvious, they will do whatever possible to stall or deny your claim. Your situation is made worse due to the extended time between injury and making a claim.
3) Do as WarbyD says, if he's in the industry, he knows just how fucked it is.
4) Document everything and do nothing outside what your treating doctor or physician prescribes. I cannot be more clear.
5) Phone calls (mainly to your workers comp insurance provider) get you nowhere. Written letters, be it requests, advice or updates on your situation well get you more speedy responses. Any phone calls you do make should be backed up with a letter confirming what was discussed.
5) I was followed on several occasions, that I observed. They are sometimes obvious, other times more discrete. If you are genuinely injured and your day to day actions reflect that, you''ll have no issues. You also need to take some responsibility for your situation if you value your health, anyway.
6) The payout system has changed dramatically in recent times. Unless, after all reasonable treatments have been exhausted and your injury has been medically declared as 'as good as it's going to get', you get $x amount based on the percentage that you are incapacitated. Ultimately, it is fuck all and will be years before you see anything like that.
7) If you change jobs, there are laws that prevent an employer discriminating against you if you have made a workers comp claim. There are also laws that determine under what circumstances you need to advise a prospective employer of your previous injury and WC claim. It's utter bullshit. Mark my works, as soon as they hear the words 'Workers Comp claim', the chances of you getting that job have slimmed dramatically.
8) Once you make your claim, be wary of your employer trying to manipulate you into leaving or resigning. The bottom line is your claim will cost them a packet, especially if you have an operation and extended time off work. They will most likely do whatever possible to reduce their liability. One such way is to get you to quit. Do not.
9) If I had my time again, based on the shit-fight I went through, I would never have made the claim. It would have been so much less emotional and financial stress, and so much quicker, to just borrow some money and get myself fixed.
10) good luck.