> The fastest spacecraft is the Parker Solar Probe at 430,000 mph

This is simply wrong. The value you provided is instantaneous velocity this spacecraft had when passing perihelion, and is mostly due to how close to the Sun it was. It has very little to do with actual velocity at which it would travel outside the solar system.

Highly elliptical or hyperbolic orbits look a bit like pendulum or a ball thrown upwards -> you have high velocity when it's deep in gravity well (eg. ball is the fastest right before hitting the ground) but the velocity drops when you're moving away (eg. the ball will essentially reach a point where it has velocity=0 before it starts falling back down). So while parker solar probe had high velocity when passing close to the Sun, it would be moving orders of magnitude slower when moving away, eg. in the direction of this nearby black hole.