Does sat/sun also decay the value of options or just days the market is open?
Yes it does!
The market prices this in on Fridays
And even better, on three days weekends and other holidays the additional time decay gets priced in causing option decay to happen even faster on the day before the market is closed.
This happens because options still have utility on days the market is closed. If there is an earthquake in Japan on a weekend and you have put options on the Nikkei index, you will still get the utility when the Nikkei drops 80% when the market reopens
Yes, it does.
Options are a contract to buy a certain asset at a certain price in the future. The contract doesn't say "but only between 9-5 on weekdays!". You can execute it any time.
The market is closed on the weekends, and likely so is your broker. But these are mainly services that facilitate trading. They are not a fundamental aspect of the trading. For example, nothing is stopping you from showing up at your friend's house on Saturday night and trading stock and options with him. You just won't have the convenience of the exchange and broker helping you actually do it. For most people, not trading on the exchange through their broker is a silly idea. But it's possible. Because of this you cannot "freeze time" on the weekend - those days are actual time value even if you as a retail trader cannot take advantage of it.