1. Yes that the right idea, just use some 0603 SMD resistors. Unfortunately without an oscilloscope there is no sure way to know that correct value as each SNES console can be different but most people just put 750ohm resistors in there and hope for the best.
2. That’s nothing to worry about, it’s just some flux residue left over from the reflow process. You can clean it off if you like with some flux remover solution but it won’t cause any problems if you leave it there.