kenhiggs
I think it was possibly 19th (18th?) century grammarians who noted that it was impossible to split an infinitive in Latin (and other Romance languages) as it was one word, so decided it shouldn't be permissable in English either. I don't think many of us still pay attention to them.
I don't understand your second point. "It" is surely a pronoun? "It's" is "it is", naturally (though it is often confused with "its" - belonging to it).
The C in rap is, of course, silent.