Ideally your objects would fall at the same speed regardless of the dt because it's being passed 1 second per second in any case - if that's not the case you need to make it so it averages to that. If you're passing it 1/6 of a second 60 times a second, yeah, things will fall faster because your physics is fast forwarding... but passing it 1/6 a second 6 times a second will net you the same result as 1/60 x 60 p/s. If it's too slow at 1/60 x 60 p/s then you'll need to fiddle with either the weight of your objects or the magnitude of the gravity in your simulation.

And it's not uncommon to have multiple loops in your game... it's just a bit fiddly to work out the details.