“Expertise” would be a gross overstatement.
I 'm a live-sound guy who’s had to deal with acoustics practically for over 20 years and who happened to once take a 3 day training in Smaart. I also had a hand in building a few rooms and trying to make the whole process just a little less ghetto.
To be fair, I always used smoothing when taking measurements because I was usually measuring for time alignment of speaker clusters and not EQ and this guy posts non-smoothed graphs. Also, I was always measuring either much bigger rooms or outdoors, so variation in results is to be expected.
The guy who posted that example of a good looking/sounding graph has some really good advice here: http://ethanwiner.com/acoustics.html. If you have the time and patients, it will tell you way more than anything I have to say
Back to the ghetto…I think your 2 biggest problems are the big bump around 400Hz which is probably local may be treatable with a single pannel at the right spot.
The crazy dips in the low end are reflections phasing out direct sound and just require better overall bass trapping. If you have some dead space above the ceiling in the attic it can be used as a bass trap by leaving an opening in the ceiling and dumping a lot of absorptive material up there. If such a space exists untreated, it may cause the bump you have at 40-50 Hz. as well as some of the other anomalies in the low end.
I am also assuming the drop at 60Hz is just your monitors naturally falling off but the point blank measurement should tell you if that is true or not.
As for the shape of your room, the sloped ceiling is probably a pro since no parallel surfaces and much less problem with room-modes. Asymmetry makes stereo imaging problematic, that is one area where headphones are are quick and reliable fix. Also, when dealing with non-acoustic sources as most people around here do, stereo is mostly panned mono sources which are not as delicate as stereo-pair acoustic recordings, where the realism of the image just breaks down if you are getting the wrong cues from your monitors/room.