The Boom plans to land at 185 knots/213MPH, comparable to a 737-800. They probably need a fraction of the distance to stop though, since the plane has about 1/3 of the seating capacity.
Wouldn't be so sure. Stopping depends mainly on how good the thrust reversers are. Wheel brakes will only take you so far (and being lighter doesn't meaningfully help you.. lighter weight means less traction.
Airliners are required to be able to land with reverse-thrust inoperative: reversers are useful for shorter taxi times and reducing brake wear but they aren't essential.
