Given that orientation, seat 55 is behind the stairwell and on the same side as the stairwell--the left, in this case--about halfway between the stairwell and the end of the car.
On my recent Builder trip, my car had an outlet on the left but ahead of the stairwell--it was in the fourth row of seats from the front of the car. That doesn't sound like seat 55 in either orientation. (The stairwell was on the left of the car.) I didn't see any other outlets, but I didn't look very hard either, and I didn't have these seat numbers to guide my search. I just noticed that one because some other guy had already found it!
When he detrained at Minneapolis, I went up to his seat to try it, but the outlet was half-behind the armrest and I couldn't get any of my plugs into it. The only plug which would work would be an extremely flat 90-degree-angle plug. In fact, I wish I'd had a chance to ask him how he even got anything plugged in there.
As to power in the lounge--there is a single outlet in the old upstairs mini-bar thing. If you bring a power strip with a nice, long cable, you will be everybody's best friend! Otherwise, it's kinda first-come, first-served, and you'll see people's cell phones charging there and the occasional laptop user standing in the mini-bar.
What I've generally seen on the SSL is... a single outlet at floor level facing the aisle, on the stairwell wall, and a double-outlet in the mini-bar (none of these ever in use by Amtrak). It is awkward to make use of any of these while actually using your laptop unless you have a long cord and are very careful with its placement. It is easy to use any of them for charging a laptop or a phone, though.
And yes, bring a power strip! Everybody will love you! You can plug it into one of the mini-bar outlets when you first enter the lounge and just remember to reclaim it before your last stop. Don't worry, nobody will take it in my experience. (And if they do, hey, it was only $10. You can buy a lot of happiness for $10 well spent :lol: )