PB Blaster is good stuff. I would spray it again before bed trying to get it into the threads, let it sit till tomorrow.
If it is still tight, don't keep turning or you may twist it in half breaking it.
Do what Hogsy said,,,,light some charcoal, put the lid on and let it heat up real hot inside. Then put the wrench or socket on it and try easy. If it wont budge, let it heat more, can spray more PB Blaster on it, but don't spray on the charcoal. Let her heat up good and try again.
Heat normally works for a rusted bolt.