What is the ruling on eating from food sent from a wedding feast where there were illicit acts, knowing that I did not attend this feast?

You were correct in not accepting the invitation because it contained forbidden elements. There is no harm in eating the food of the walimah (wedding feast) if it is lawful and good. What is forbidden is attending the reprehensible act or participating in it. Otherwise, the walimah itself is permissible. It is permissible to eat if the invited person knew about the reprehensible act but did not see or hear it. And if it is permissible to eat with the presence of a reprehensible act, then eating after it has ended and disappeared is even more permissible.