I was wondering, do you think Shylock is jealous of Antonio and Bassanios friendship? Is this why he is being cruel?
Shylock's principal motivation of hatred for Antonio is based on several factors, including Antonio's hatred of him, Antionio's lending money without interest (and thus hurting Shylock's business), and Antonio's religion. He himself says he hates him for no reason.
One possible connection with your idea of jealousy, is that Shylock is jealous of Antonio's standing in Venice, and the fact that Antonio has friends like Bassanio at all, while Shylock is disliked
No, there was other reasons for his anger towards Antonio. He hates Antonio for lending out money to people without charging any single interest, bringing down interest rates on loans in Venice, which is quite inappropriate in business industry. He also detests him for being a "Christian", but I think the main motive behind the sudden outrage against him was actually due to the hatred that Antonio show towards him, which he was being spat upon and treated like a dog, a servant by him, laughing at his failures and mocking against his victories, seemingly to taunt his every actions, trying to put him down, shame him in front of people, so he was trying to seek out vengeance for the disgrace that he had suffered and it was payback time.