What production did you see? I tend to be of the school that Shylock is a racist stereotype who gets more sympathy than you would normally expect (especially compared to other racist stereotypes of the same time and place) because sympathy is what Shakespeare specializes in. But Shylock is still a villain, and it's not entirely because he's a Jew. He's a bad person who does bad things, and . . .well, the bad things he does are linked to his Jewishness but they're not JUST his Jewishness. I mean, I don't know if that makes the text less offensive, but I think people who want to make Shylock out to be a tragic hero have to kind of ignore the part where he tries to use the law to commit murder.

And yeah, Antonio/Bassanio is basically canon, and not just in the way slashers always say that. I think the relationship was deliberately implied by the text.