Q: At what point can I pull a waivered player back off waivers?
A:: You can revoke the waivers at anytime after he was claimed by another team.
Q: Do I have to wait till the initial 72hrs has past after the player was posted on waivers to post an agreed upon trade?
A: Yes, the initial 72 hours has to pass before posting a trade because all teams have to be given a chance to make a claim. Since you're an AL team, AL teams will be given priority over NL teams, based on W-L records.