OP, this is such a difficult one.
We kept DS in our room until he was 5.5 months then, exasperated with all of us disturbing each other, put him in his own room. Having said that, we did put him to bed on his own for an hour or so before we went to bed from about 2 months Until about 4 months DS was very Velcro and I couldn't eat a proper meal, sometimes DH was working away so we couldn't do shifts. I also was bring treated for PND and anxiety and getting an hour on my own in the evening was recommended, even considering the SIDS advice.
Conifer, I don't think doing that was a selfish act. To be able to care for DS and breastfeed him (thus reducing the risk), I needed to eat properly. I also believe it isn't advised to let a baby sleep on you on a sofa for safety reasons, although lord knows, we've all done it. Even when you thoroughly explained, you were still being very judgemental, you need to understand not every baby is the same and the same thing simply does not work for everyone.
FWIW OP, I know someone who is a very highly trained intelligent medic. She read through the studies and made a decision that, for her babies, it was better for all of them for them to be in their own room. I think (I am not medical) the thinking behind it is that the CO2 you breathe out encourages the baby to breathe, certainly it is having someone else breathing in the same room that is the reasoning.
I think no matter what happens, even if your DC simply has a bad night it is only natural to second guess and question yourself. I find the only way to get through is to make an informed decision as possible and work that with what works for you.