But how does this relate to eating blood? Genesis 9:4 was before Jews and the Law of Moses, it was before the separation of Gentiles from Israel. This was commanded to Noah and all of his descendants. The dietary laws of Israel came later...
I think what you might be missing here is that anything that came of revelation prior to Moses was still "the Law". Now we often think of "the law" being what applied to the Jews; but Paul tells us that "no flesh is justified because by the law is the knowledge of sin". Romans 3:20.
So reason would have it, that "the Law" was still in operation before it was expressly written down. It bore witness in the conscience of men as well as the witness of creation. So therefore every human is still accountable because even if they don't have the express written revelation, they have the witness of creation as well as their conscience.
Reformed theology often speaks of 2 covenants. The "Old Testament" and the "New Testament". You are either covered by the blood of Christ or you are "under the law". Personally I'm starting to wonder if it's more of one covenant; seeing how the "the law" (penned OT) as well as "the Law" (conscience, creation and penned OT) only points us to the Redeemer to come. So basically we have one covenant and the shadow of that one covenant.
And so getting back to behavior and motive; of "meat sacrificed to idols, blood, strangulation and fornication". It's an interesting list. Are you engaging in an activity to the end of idolatry, or are you engaging in an activity to the end of the glory of God? And aint it interesting that the two major aspects of human behavior that are addressed here are eating and sex? One engages in both (one or the other) either as a matter of idolatry, or to the glory of God.
Side note here: I've come to the conclusion that the notion of "marry so you don't burn" is not really speaking of lack of self control sexually; but more "burning" for things that are right and good in God's eyes that are related to marriage. People want companionship. People want children. People want families. And all that is far more than - gee, I can't stop myself from having sex. Someone who's "in the game" for that reason only, has other more serious problems. Marriage doesn't automatically sanctify someone's sexuality, if they are off in motive to begin with.
So just as this motive can be off (actually being idolatry for as being "to the glory of sex" as opposed to the glory of God) so can the motive for consuming food. In the case here being connected to false religion. Granted one can also commit idolatry being addicted to food; but that's a different issue.
And so here are the prescriptions around. Fornication is an act someone does of their own volition. It's not like if you go to someone's house and they give you something that is not prepared according to a specific religious prescription (you're free in Christ to eat it anyways).
So reason would have it contextually speaking that since fornication in the passage is done of one's own volition, so would be sacrificing meat to idols, drinking blood and strangulation. If one does that of their own volition, committing idolatry in the exercise of consuming food; that is the prohibition, just as in fornication one is committing idolatry in the exercise of sex.