I have a 9 month old and remember when she was about 3 months she didn't seem to sleep much during the day either. My daughter was born at home, and is a "natural baby", meaning we aren't big fans of anything that is pretty much just natural. I breast feed her (still) and have just started her on only a few solids. This information is important only in that it helps to understand the environment our daughter exists in.
Over the last 9 months her sleep schedule has changed many, many times. She too slept through a good few hours at a time early on (just a few weeks old) and seemed to set a schedule for herself right away.. then abandoned it and left me wondering and not knowing what to expect from one day to the next.
I know a lot of people will tell you, along with docs, books, etc., that babies need something like 14 to 18 hours of sleep a day (at that young age), but mine didn't. And because I had the luxury of staying at home with her (and am still) I didn't push her to a schedule.
I would suggest just watching for your little one's cues. Is he rubbing his eyes yet? My daughter's eyebrows become pink/red when she's tired. Your son will let you know when he needs to sleep and as he grows, you'll start to see a pattern, but watch out, because often it seems the moment you think you've got his new sched figured out, he'll change it.
Trust your instinct and don't worry too much (this early) about establishing a routine for him that you can count on. He has a sort of routine that suits him, and it is constantly modifying to match his changing needs, and he will increasingly let you know what he needs.
And soon, you will see him very obviously recognizing his surroundings, if he doesn't already, and that will comfort him which will encourage him to rest when he needs to. You mentioned swaddling/blinds, etc.. One thing I did notice, especially when mine was very young, was she did not want to sleep if I was busy with something, even work on my laptop. I had to all but stop everything and just calmly sit with her until she fell asleep and then I could get up and work.
My best suggestion is to just "roll with it", meaning whatever and whichever direction your son leads, follow. As he grows, you'll be able to encourage a schedule of some sort based on his habits, but chances are it won't be the sort of schedule you might expect.
Example of my daughter's schedules:
0 to 2 months (or so) - she would sleep 1 - 3 hours at a time. She co-slept with us and breastfed throughout the night and day; I could sometimes get a 4 hour chunk at night of sleep at a time.
3 to 5 months - Bedtime was no later than 8pm, for all of us. We'd get up around 7am and by 11am she was out of it for most of the afternoon.. She would wake up to nurse, but for the most part she would dose until 4pm, then go back to sleep about 6 to 7, then by 8 or 8:30 she was ready to retire to our bedroom.
6 - 8 months - She preferred to be in bed by dark. She would get up around 7, go back to sleep an hour or so later, sleep for an hour and be up til 1 or 2pm, then sleep for another hour, and then be awake until bedtime. (Teething totally threw that sched off... teething causes her to nurse constantly and sleep as much as possible.)
9 months to current - She can stay up til 9 but if we don't "put her to bed", like, in her crib and follow bedtime routine, she gets beyond tired and then it's 11 before I finally get her calm and asleep, and it invariably requires nursing and Daddy walks... But, if I get her to bed by 9, she will nurse about 2am, then again at 5 or 6am and sleep through to 9 or 9:30am if I let her... then she sleeps all afternoon (1 to 4ish). She is crawling and walking now, however, and has three teeth, and seems to sleep more now than she did at 3 months.
Hope some of our experience helps in your situation.