[LeGrande]

Newton’s laws work fine in reference frames moving at relativistic constant velocity, as long as you make the measurements inside the moving frame.

I don't think that Newtons laws are applicable to an event horizon, which is within the "moving" frame.

If you make measurements on an object moving at relativistic speeds and you are measuring from the earth’s frame, then the Lorentz factor must be used.

That is correct. You don't use Newtons "laws.' Newton couldn't nail Mercury's orbit, Einstein did.

[camerakid400]

If an object is moving at constant relativistic velocity (not accelerating) and you are moving alongside the object in its reference frame, then you are at rest with respect to that object. Newton’s laws then apply.