How fast is Miller's planet orbiting Gargantua in the movie Interstellar?

In the movie Interstellar, Miller's planet is so close to the black hole that it experiences severe time dilation - one hour on the planet is seven years for every one else.

The planet is (presumably) in a stable orbit around the black hole and in no danger of falling in any time soon. Otherwise, it wouldn't be a very good candidate for new Earth. Thus, it must be speeding around the black hole very quickly to have enough angular momentum to avoid falling in.

Given that the gravity is causing such a severe time dilation, how fast are they travelling?

I suspect that it is very fast since even at 90% of the speed of light (something we are not even close to achieving for macroscopic objects), there is little time dilation.

EDIT: I was incorrectly equating time dilation due to speed with gravitational time dilation, so ignore the above sentence. They are related, but not in the way I suggest.

So, how fast did they need to accelerate the ship to match Miller's orbit and land? And again, when they take off, they would need to decelerate to match that of the mother ship. Wouldn't that delta-v have used up most of their fuel? That alone should have precluded them from attempting to visit this planet until they exhausted Mann's and Edmund's planets.

Highly related question: Since there is such a severe time dilation, if you measured your speed while on Miller's planet, you'd see that it was substantially higher than when measured from the mother-ship.

Would the planet appear to be orbiting the black hole very slowly from the perspective of the mother-ship, even though it is orbiting very fast?

Does that mean that as objects fall into black holes, outside observers perceive it to take longer for the object to fall in due to the time dilation? I believe this is the case.

So as the Endeavour approaches the planet, they would perceive that the planet is accelerating and would need to speed up to catch it. Bromily from the mother ship might see them as travelling a constant speed, or (most likely) even slowing down as the approach the planet, when in reality they are accelerating towards it.

Likewise, when they leave the planet, Bromily would see them very slowly coming towards him, but accelerating as they got nearer. In reality, however, they would be decelerating to match the speed of the mother ship.