Murray, Murray, Murray. 54 Is young, if you join an online dating site, especailly one with a shitty reputation like POF you'll hook up with some chippy in no time. Just make sure they don't use you for your money and proceeds from the breakdown of the relationship you're currently in. I think you've been there and done that one already, eh?
Buck up, hitch up your trousers and leave the dead end you currently find yourself in. Why would you stay there when you are so unhappy? There's no magic pill. You either have to change your life or change your state of mind. Figure out which one is the easiest route to happiness for you either leaving or accepting and being content where you are... take the first step to the rest of your life.
“The willingness to accept responsibility for one’s own life is the source from which self-respect springs.” ~Joan Didion