You’re really putting the clerics in a tight spot. If they recognize the discouragement of vows & oaths, where does that leave marriage? So they have to conjure an illusory ban on ‘swearing’.
There’s a useful paper, “Oaths, Vows and Trust in the Bible” — which seems to clarify that marriage was not viewed as an oath. It was a simple contract (with divorce simply being the dissolution of a contract).
On obscene speech, I was surprised to read in Jeremy Hultin’s The Ethics of Obscene Speech in Early Christianity and Its Environment that there is no ban on it anywhere in the Bible, which distressed Judaism at various points, as the prophets especially have very graphic sexual speech.