Modeling it as two spheres, one 16 km across the other 12 km, with a density the same as water, its total mass would be about 3*10^15 kg. At a distance of 8 km from the center of mass, the escape velocity [0] would be about 7 meters/second or 16 miles/hour.

But the asymmetry of Ultima Thule means that its gravitational field would be weird. Not like a sphere at all. So the acceleration of gravity and escape velocity would vary a lot from place to place.

[0] https://en.wikipedia.org/wiki/Escape_velocity

Probably not, from the approximate sizes noted in the article it sounds like Ultima Thule is a bit bigger than Diemos, which XCKD says you could escape with a bicycle and a ramp.

And just for fun, I also worked out a best guess for the force between the two "lobes": 1.5 x 10^13 N (assuming Ultima Thule is the same density as our Moon), which is about equal to the (Earth) weight of all the ships in the world. [0]

[0]: https://what-if.xkcd.com/33/