1. Yes, Paul knew, he was there according to Acts 15 and hears about it again in Acts 21 when Paul returned to Jerusalem and faced charges that he was teaching the Jews who live among Gentiles to reject Moses. (Quotes from the CEB)
Acts 15:2: The church at Antioch appointed Paul, Barnabas, and several others from Antioch to go up to Jerusalem to set this question before the apostles and the elders.
Acts 15:12: The entire assembly fell quiet as they listened to Barnabas and Paul describe all the signs and wonders God did among the Gentiles through their activity.
Acts 21:18 On the next day Paul and the rest of us went to see James. All of the elders were present.
While this council affirmed "On the contrary, we believe that we and they are saved in the same way, by the grace of the Lord Jesus” (Acts 15:11); also imposed a few rules from Moses that are repeated three times in Acts.
Acts 15:20 avoid … Acts 15:29 refuse … Acts 21:25 avoid …
the pollution associated with idols refuse food offered to idols avoid food offered to idols
sexual immorality blood blood
eating meat from strangled animals meat from strangled animals meat from strangled animals
consuming blood sexual immorality sexual immorality
Acts 15:20 τοῦ ἀπέχεσθαι … Acts 15:29 ἀπέχεσθαι … Acts 21:25 φυλάσσεσθαι αὐτοὺς …
τῶν ἀλισγημάτων τῶν εἰδώλων εἰδωλοθύτων τό τε εἰδωλόθυτον
καὶ τῆς πορνείας καὶ αἵματος καὶ αἷμα
καὶ τοῦ πνικτοῦ καὶ πνικτῶν καὶ πνικτὸν
καὶ τοῦ αἵματος καὶ πορνείας καὶ πορνείαν
2. Paul does not make any reference to this decision when he writes about εἰδωλόθυτον in 1 Corinthians 8(:1, 4, 7, 10) and 10(:19). He does not prohibit it.
There are some with "knowledge." They know that false gods are nothing. The food has been sacrificed to nothing, so there's nothing wrong with (probably going to the pagan temple) and eating food there.
There are some who don't have this knowledge, who believe that such food was really dedicated to a false god. They cannot eat it. To illustrate the power of forbidden foods, a former Muslim talked about the first time he ate pork. He didn't know that it was pork. An hour later he asked about that meat. They told him it was pork. His body reacted. He vomited. My wrestling coach had a similar experience when he learned that the food he was eating in Japan was slug.
Food issues involve more than just knowledge in our heads.
While Paul doesn't talk specifically about εἰδωλόθτον that could be the context in his comments "One person believes in eating everything, while the weak person eats only vegetables" (Romans 14:2).
Paul confesses: "I know and I'm convinced in the Lord Jesus that nothing is wrong to eat in itself. But if someone thinks something is wrong to eat, it becomes wrong for that person" (Rom 14:14). [Note that "wrong to eat" is the CEB's translation of κοινός. Generally, it refers to "what is common, ordinary," but in regards to the cultic, it is often in contrast to what is sacred, consecrated, and thus can mean "profane" or "defiled." We continue to make this distinction between the consecrated bread and wine of the sacrament, and "ordinary" bread and wine that we eat at other places.]
I believe that this verse was the background for listing four positions within the ELCA in regards to same-sex relationships. For those who consider them wrong, they are wrong. For those who consider them acceptable, they are acceptable. I also see it in the LCMS in regards to women's participation in worship. Some think its OK and women read some lessons, etc. Others do not think it's acceptable, so women do not read.
Back to the main topic. Paul does not seem to indicate any knowledge about the Jerusalem Council's decree, which in participated in, according to Acts. Rather than advising Gentile believers to refuse to eat food sacrificed to idols; he indicates that he can be acceptable for some to do so - those who have the knowledge that they are nothing. He also puts himself into that category.
He seems to have had no knowledge of the prohibition against eating food that had been sacrificed to idols; or, if he knew, he disagreed with it.