I am sorry for your situation. I am not sure what the PA laws for recording phone conversations. Verify with an attorney as a recording may help in a proceeding first to get you a restraining order and second for custody for your minor child.
The above answer does not constitute an attorney client relationship and/ or retention of counsel. This answer is based upon the facts presented and may change if additional information is provided. The rules of the Bar for New York State may require me to advise that this could be construed as attorney advertisement.
Based on the content of her text messages, her behavior may rise to the level of abuse under Pennsylvania's Protection from Abuse statute. You should have an attorney review the material. If you do not have a custody order in effect, you should consider seeking one from the court -- that way you can address what behavior is appropriate in front of a child. It sounds like you are on the right track by not retaliating and ending the conversations as soon as possible. I have written several pieces on my blog about Pennsylvania's Protection from Abuse statute.
These comments are intended as general information and do not constitute legal advice.