Others will have details, but DO NOT force the tank into a distorted position. They tend to crack when the floor gets weak and the toilet wobbles with somebody sitting on it. Based on that, it doesn't make sense to assemble the toilet to the tank with a tweak in it.
The common flanges are Female Thread, Male Thread and Glued. If you could turn it, must not be glued. You could probably unscrew it and see what needs to be done to drop the level of the flange.
Again, others will likely have better suggestions