Yes, a black hole with the mass of the Earth would be much smaller. There's an actual size illustration of one in the article.

The gravitational attraction from a given distance from the center would be the same as for Earth. For example, if you're 4,000 miles from the center, you'll experience a 1-g acceleration. The difference is that, because of the black hole's smaller size, you can get a lot closer to it.

No at a distance it would be exactly the same. You would only start to notice the difference gravitationally once you get to be around 1 earth radius away.

The Schwarzschild radius is determined by the mass of the object, not the volume.

Radius = (2 * Gravitational Constant * Mass)/(Speed of Light^2)

Not my area of expertise, but at the distances we're talking, can we just treat them as point masses? Somewhat different accelerations of earths colliding won't matter much until the density is comedically low.