What was Paul referring to if not the same sexual acts that the homosexual men he was discussing previously?
You're correct, reading it in context is important. If one starts pulling phrases out of the Bible they can make it say anything they want. So in context here Paul is referring to lesbianism and homosexuality.
means that it is something other than normal sexuality, no?
Any sexual activity outside the bound of marriage is against the design/intent. But within marriage I'd have to agree with those who say the Bible is silent on the topic. The exception being 1Cor 7:3,4 - and that is just saying it must be consensual.
If I wanted to push it I'd say the phrase "Let the husband render to his wife the affection due her" is not referring to plain-old intercourse. But I won't go there.