"Not something you really wanna be lookin' at." - Lou
Just like Dr. Psychodramaturge telling Sheila that half of Damien's desire to be a firefighter is based on her objection, you knew that when Lou told Tommy not to look at the 9/11 footage he would anyway. Forbidden = fun. Of course, having Genevieve whisper lord knows what into Tommy's ear didn't hurt either. Whatever she muttered was probably fun too.
As shocking as the news footage is, the fact of the matter is nothing has changed. Jimmy Keefe is still dead. However, how and when he died are now the issue. Why wasn't he in Tower 1 when it collapsed on 9/11? Why did he leave and head to Tower 2? The events of that day are indescribable, and "hectic" doesn't even touch upon how unmanageable ground zero was. Jimmy was just doing his job.
As for Tommy, it obviously puts him in a situation where any blame he already carries is only intensified - could Jimmy have lived had Tommy been with him the whole time? Sure, it's definitely possible. On the flip side, Tommy could be dead right next to him.
What's more important is how this is going to affect Sheila. As she tries to purge herself of all thing and thoughts Tommy Gavin, finding out that her husband didn't die when she thought he did, eight years after the fact, isn't going to help. It's either going to bring the two of them closer or push them apart even farther. Which is it going to be?
Consider Damien. Sheila isn't going to lose her son the same way she lost her husband. Pushing away Tommy won't be the answer. Mick was right - that footage, seeing Jimmy, is only going to send Tommy down an all too familiar path, and Sheila has always been a part of that journey.
A few more thoughts on "Jimmy" --
It doesn't happen frequently, but seeing Lou flip out always makes for a good scene. I always think of Lou as comedic relief, but John Scurti has had a handful of seriously poignant speeches in this show over the past four seasons and they often get overlooked.
I'm not sure who's stupider - Tommy for getting Derrick a job as a barback or Derrick actually taking it.
As the episode ended, I couldn't help but laugh at Mike's bar, not because of all the headaches he went through to open it ("Lumberjacks," un-blacking the place, bribing the liquor authority rep), but because of how easy it's making Tommy's freefall. It's like Tommy asked, "what's the one thing my friends could do to screw up my life more" and they did that exact thing - open a bar. After Tommy's last meeting with the psychic when she told him that Jimmy wants him to know the truth, if I were Mick, I don't think it's Derrick I'd be so worried about with a bar full of whiskey under his nose.