WD40 wont do shit, it's not a penetrating fluid. Is's (WD)water displacement! (40) is how many times it took the guy that invented it to get it right lol. Basically the main pourpose of it is to prevent corrosion from starting, but once corrosion is in there its not really good for anything.
Try some PB blaster man, it just works and if you can twist the bolt any while soaking it, do that also. But if for some reason your bolt is slightly bent, you need to cut that shit out.