Even if it was a solid ball of iron, how much could it's gravity have been anyway? maybe if the Enterprise were moving at a slow walking speed.
We're witnessing a scale discrepancy in such scenes anyway: despite dialogue, such rocks aren't thousands or even hundreds of kilometers away. But perhaps we're to believe that they are, in which case it basically follows that they are also realistically large rocks with lots of pull.
Riker asks how he could have done it. How about Danar signaled lower a force field without first identifying himself or providing some kind of authorization code?
Doesn't sound likely, because why wouldn't the system ask for an ID? In which case Riker's amazement is appropriate, and Danar is astoundingly clever.
That's what the writers want us to believe, so why not believe them? We have to commit a double fault if we want to believe that Damar did something trivial and Riker is not entitled to express wonder.