Why did Mr. Chow act like the $80 grand was HIS...?

It is rightfully yours UNLESS you have debts to pay. In society, if one owes another something (usually financially) and/or does not make it, so another has to pick up the tab; they are property and in debt to that other person. When you are in DEBT to someone, almost all your freedoms are lost AND the debt must be repaid.

The common exception in today's society though is being a woman. In that case, you were treated like property pre 1960s and they won out. Everything they make is theirs and guys have to pay for most things. Even if women are in debt, you will see that they can sue the guy or seduce him for a rape charge to get their "share" of their money (even as the guy made most of it).

THERE IS NOTHING TO FEAR. COLLEGE FOOTBALL IS HERE!!!

It was Chang's winnings. Alan was playing Craps and was hot and Chang played the streak and won 80 grand. Chang put his money into his purse, but Alan, being blitzed out of his head, thought it was his satchel.