1) Your wife left you, and so far from what I've read, without giving you a valid reason. 2) She avoids all talk about your relationship, besides that she is done. She does not want to talk to you about anything.
Do not initiate any money, relationship or marriage talk. The only "conversation" you are allowed to initiate is about your son. Fight the urge to be her knight in shining armor. If she needs or wants your help she will come to you. She is an adult, so treat her like one - even though she is not behaving like one.
Since you are avoiding paying for legal advice or pursuing a legal separation then it's time for you to treat her like an adult.
Let her live up to the consequences of her actions. I'm not saying "Don't help her." She is the mother of your child and its your duty to see that your son is taken care of. So help her when she asks for it.
As for the debt issue. You know that you are liable for it. It may be in your own interests to initiate a legal separation. Why? Because she is behaving irrationally. Document all these actions for the future in case things don't work out.
M:11 | T:12 | Status: Married 4C's of WAS communication: Cool, Calm, Collected and CONFIDENT