If this dream wasn't scary, it sounded awesome! Did you feel powerful fighting the demon angels, or somewhat helpless? I think how you felt can be a big hint about what this dream was about.
Because the dream starts off in such a normal and comfortable setting, I believe this dream may be about a problem that affects your normal life. Maybe it represents an inner fear that you feel at these comfortable times? Sometimes, we can fear
losing that comfort and that anything could go wrong at any second, which might be represented by the lights suddenly going off. Have you been anxious lately?
Sudden fights in dreams like this might be an outlet for your instincts, such as how it's believed animals dream of fighting and catching things. Unless you feel this isn't true, then it most likely isn't. I notice that these demons are very thoughtful and think about their plan of attack. Could they represent fears of people you have in your life? Do you fear or are these people invading your life as well? There's a chance they could also represent your own mind. Maybe a "dark" side of your mind which thinks things out logically to cause problems for yourself?
I know some people dream of demons more often than others. I've never had very many dreams with a straight-out demon creature, so I can't say what it is that causes these. I think people who have deeper fears than most, such as people who have witnessed a lot of dark things in life, have dreams of demons more often. I had a family member who had constant dreams of demons, and he had a ton of experience with seeing bad things happen to people

. Maybe that's where the demon imagery comes from? Of course, it's probably originally taken from things like movies and books, but I think the image fits well with our mind's idea of a person with a lot of injuries or is strange looking? With you, could it be that you just took the images from something from media? Also, do you have a lot of dreams with demons, or is this just a very rare occurrence?
Since you were able to hit one demon that wasn't paying attention, I think this means your mind is telling you that you are able to defeat whatever these demons represent if you pick your battles wisely. Also, what the demons represent could change throughout the story. I think a lot of it depends on your feelings at the moment and where the demons are and what they are doing.
I think the lights going off are continuing this theme of ominous mystery surrounding your safety. Is there a fear of things suddenly going bad in your life, or do things suddenly go wrong often?
The fact that the only lights left on were ones in the bathroom or office might mean that in your life, things could be going normally in the parts of your life that aren't useful to your or are useful to your enemies.
I think the choice at the end of fighting back these demons represent your mind telling you that your only chance to deal with this problem in life is to remove it before it gets any worse, as it will grow and grow. Well, maybe.
My dreams often end before reaching a climax as well. I wonder if it means that the dream's about dealing with emotional problems and choices rather than just a story.
Good story though! The action sequences were fun to read about.