1. Since the Math SPU is affecting the skill and not the attribute, it should affect tests involving the Resonance attribute.
2. The reduction is a bit trickier. As a GM, at my table, I would allow it, since the only restriction to the reduction is that it can't reduce it lower than 1 Edge cost, and only lowers it by 1. Since you can't combine multiple boosts/actions per character action, I don't see it abusing Edge to allow the reduction on the same boost used multiple times. However, that is my GM prerogative, and not an official stance (that's above my pay grade).