In spite of all this hatred, what is Shylock still prepared to do for Antonio? Why?

This depends where in the play you are referring to. Shylock says he'd would like to be friends and lend the money for free providing Antonio put up a pound of his flesh for collateral.

I'm referring to Act I Scene 3

Yes, Shylock is prepared to do forgo any monetary fee, for a pound of flesh.