Thank you very much for the paper! It is interesting read indeed. But:
Selfish mining is not relevant in Ouroboros, since, as you mentioned, the fixed time-slots. And these slots are actually solve a lot of possible problems. So most of possible vulnerabilities know for other systems are just irrelevant in Ouroboros, which is why it’s awesome and exactly why, I think they developed it like this 
But still thank you for the paper! Knowing all this stuff is still a good thing for anyone interested.
UPD: Just for context - this whole thread: