Several of Antonio's friends reognize him for his generosity. It is said that he has on several occasions lent or given money to friends and neighbors, particularly those who have found themselves debtors to Shylock and his colleagues. So, why exctly does Antonio need to go to Shylock in the first place? Is there nobody in his community that would be able and/or willing to help him out?
One theory (just putting this out there): Antonio does not feel comfortable asking his friends for assistance, whether or not he has done anything to earn their respect or their friendship. He would rather go to a career moneylender, despite his disdain towards them, simply because he will not have to plead or justify himself.
It's because all his ships are out at sea going to sell his merchandise — until they return with a profit, he doesn't have any cash to give. This is why the sinking of his ships was such a big deal.
Evidently, there isn't. Maybe Shylock's method of making an honets profit for yourself is more secure than relying on "friends" to whom you've been overly-generous. Ayn Rand wouldn't be surprised.
It was very much a Literal Genie interpretation of the contract: A pound of flesh from the chest, to which the stipulation of "without drawing a drop of blood" is added. Sure, Shylock can take his chances skinning him, but with a very hostile crowd and magistrate in view, would he really take the chance?
Alternately, Shylock was screwed as soon as he tried to go to court in the city where the word "ghetto" comes from (it was the part of Venice where Jews were forced to live in). Ain't no way a Christian court would let a Jew win over a Christian