Is it bad if my cast that was tight on my leg and ankle at first is feeling loose now and I can move it?

Both Surgery and inactivity will cause your limbs to swell up. As they heal and you start moving around the swelling in your extremities will go down, so what you are describing is perfectly normal.

No this is normal there are a couple factors that cause this, one is swelling in your ankle and leg from the injury and surgery, as you heal this swelling goes down and thus the cast is looser also it is normal to lose a bit of muscle and water weight while in a cast ,completely normal for the casted limb to be a bit smaller than the uncasted one when the cast is finally removed (you will gain this back as you use limb once you are all healed) When you go back for x-rays they will determine if the cast needs to be replaced or not (too loose)

No the swelling is going down. It is normal for a cast to loosen up. When you go in for your check up they will decide if you need to be re casted or not.