It is right and lawful to pay debts that you owe. The boat was older and appeared to need work from the start. A long voyage places major strain on all parts which is why real cruisers replace worn parts and carry plenty of spares. There is no indication you did either. The list of repairs needed is rediculous! You have a USED boat.
Your husband sailed with the captain so if there was a problem you should have paid the captain for the work he did to that point and find someone else. Since you did not it was your acceptance of his skills your insurance company accepted him as well. Then after completing the delivery despite the boat breaking down numerous times and his repairs enough to finish the job- NOW you refuse payment! This is unfair, unthethical and I'm sure unlawful. You are inexperienced and have no idea what reasonable use is on a voyage. You need to take the messages to heart from experienced cruisers, pay what your captain is owed!