I noticed that Rashi says, that when the angels visited it was in fact Pesach, and I think Alshich says Sarah made matzot in fact. Afterwards it says Lot gave the angels Matzot. We are told that the Patriarchs kept Torah even before it was given. But I find it hard to believe Lot was so righteous to do this, especially when we see how he acted with his daughters after the destruction of Sodom. Was Lot also considered righteous, and did he keep Torah in fact?

Lot was righteous, relatively that is. That’s why he was saved and Sodom was destroyed. When our sages say that Lot kept Pesach, that is not necessarily in the literal meaning like we celebrate it today. It is one way of saying he was heavily influenced by his uncle Avraham and practising his beliefs and values.