Truthfully, the best thing you can do is hire an attorney who will expedite this matter on your behalf. Not only will hiring an attorney show your soon-to-be ex-wife the seriousness of this matter (as up to this point, it seems she thinks it's just a game), but it will also force her to appear in court if she wants to continue having custody of your son. You can find an attorney through the American Academy of Matrimonial Lawyers website. Either way, whether she shows up for court or not, you will be granted a divorce.
Also, if you are interested in seeing your son again, an attorney can help you file the necessary paperwork to force your soon-to-be ex-wife to allow you visitation or joint custody. Best of luck.