Lol, this is a very harsh situation be into... First of all, I would try avoiding as maximum as possible to spend money which doesn't belong to me. When the person does this, it's inevitable to no be seen in a negative perspective by the family and everyone else, because it's an action similar to stealing or betraying someone... I fear he is only going to be able to retrieve his reputation and respect towards his father by replacing all the money lost somehow.

He may work and accumulate money to repay his debt with his father. If he is able to do this, even though it takes a long time and a lot of effort from him, I'm pretty sure his father will forgive him and start to respect the son once again, because he has shown to be worthy of through his genuine efforts in an attempt to fix his previous mistake. Maybe he doesn't even need to repay the whole debt, but only his good will can be already enough to show his father he deserves to be trusted once again!