Bullets from a recently fired gun are extremely hot. Regardless of the force that might slow them down in just a few feet, Bo would burn his fingers if he picked one up.
When Bo goes to pick up his sister from school, the administrator tells him that she was released to her uncle, who turns out to have actually been Angelo. While kidnappings from schools used to be common, districts now are very strict about releasing children to designated guardians specifically identified to the district.
The plot climax relies on the power of an electron magnet. The power pack and the wires are all to create a more powerful magnet. Magnets work on substances with iron in them. They have no effect on plastics or nearly all other metals, such as lead or aluminum. Bullets usually lead or brass and certainly the bullets used in the gun at the end would not have been affected by any magnet.
The shadow of the cameraman is visible as Bo walks away from the police.
According to Bo, the negative is fed to his thumb, and the positive to the rest of his fingers. When the electromagnet is engaged (particularly after he "magnifies the voltage") it would cause his thumb to attract to his fingers, in the fashion of the Italian hand gesture. Bo never forms this gesture in the movie.