What has Boab's dad actually got to do with the ticket? The verbal agreement is between you and Boab and boab and claire. As it's only a Civil matter he can't demand you present him with the goods, no-one can really, hence why web shops can offer you a refund if they can't get you the goods.
I, personally, would either write him a cheque and take a photocopy of it or wait for him to take small claims proceedings. He'll have to pay the initial fees to take it to court, then probably get laughed out. He'd be lucky if a judge didn't award you with compo for un-due stress caused.
Any threatening behaviour can be classed as common-law assault, “any act which puts a person in fear of immediate and unlawful violence”, and can be punishable by prison time, especially over civil matters that get out of hand.
Don't let it get to you mate, the law is on your side and he'd be an idiot to go any farther.
Good luck.