I think you already know that practically, it is pretty much impossible that you will close the gap at your current company. The fact that such a large gap has persisted over multiple years demonstrates that your management doesn't reward performance in a competent manner.

If you land a position at a Big 4/5, you can expect to make 300k+ (total comp), and still retain flexible work hours, PTO, etc. Competition for dev talent is fierce, and with good interview / negotiation skills, it is possible to make integer multiples of your current comp without sacrificing perks such as a good team and flexible hours.

Also, read this: http://haseebq.com/how-not-to-bomb-your-offer-negotiation/