The 210 range is about normal. With it reading a bit higher it may still have some air in it somewhere. And yes, leaving the cap off overnight couldn't hurt. When you were bleeding the system did you have your heat set to full hot and fan on full blast? There could be some air trapped in the heater core.
I think someone mentioned jacking up the front end to help with bleeding. I'd turn the heat on full blast, let it idle until you hear the fans kick on and then crack the bleeder and see what you get.
Don't forget to fill the overflow bottle to the hot or cold marks (depending on the temp of the motor). If it's empty I could see it adding air back into the system.
