The best way to become the Lighthouse is to start making a great life for you and your son. What kind of man do you want to be? Instead of worrying about who dumped who????? Start mapping out a awesome life for yourself. Then maybe someday down the road (years most likely) she may want to join you.
Dude I know it sux but you just started this journey and is likely to go on for a very long time. Now you can wallow around and feel sorry for yourself or you can roll up your sleeves and start doing the hard work.