My heated bed started separating (maybe due to overtightening of the 4 screws I have). My model is the Prusa i2. There is maybe about 1 millimeter of lift on the middles of the print bed in the middle of each side. For right now, I can only print on the lower coordinates (x:0-60mm)(y:0-60mm) without having adhesion issues due to the hotend ramming into the previous layer on one corner. Is there a way to winch the layers back together? I have glass on top, but I fear that the binder clips fastening it are slightly bending the glass plate.

This is a PCB heated bed I assume? The only real way to get a flat print surface if the PCB is out of whack is to clamp something stiff on top of it. I have found that glass often isn't stiff enough (at least when it's ~3mm or less thick) and will flex enough to make printing difficult if the PCB underneath is significantly warped.

Your best option would be to pick up a new heated bed from a reputable supplier if you can afford it. Don't get just get the cheapest one you can find on eBay, they can be really hit-and-miss as to quality, and in some cases won't work at all without modification.