the_leander wrote:
I've tried correcting him (something his mother refuses to do) but to no avail.
Then clearly she has an agenda. I think you really need to talk to her. Let her know you're not a threat to her new relationship, or the relationship between her, her partner and your son, but that being recognised as the father of your son is important to you. Turn it around on her and ask her how she would feel if she was denied the identity of his mother. Maybe then she will understand how you feel.
the_leander wrote:
I honestly don't know how much more I can take before I crack on this.
That's understandable, but I think it would be a mistake. Show her you are upset, cry if you want to/need to show her how hurt you are, but don't lose your temper. That will just give her reasons to keep you away from your son. Hard as it is, you need to be calm and dignified. If she is unwilling to respond to that, then perhaps you need to arrange some kind of family counseling. A mediator may be very helpful in communicating with her and ensuring a reasonable response.
My dad used to mediate Family Group Conferences. They are basically opportunities for families with problems to meet with a mediator to discuss their problems. The mediator ensures the meeting doesn't descent in to arguing, and encourages the family to compose outcomes which suit the whole family. They meet weeks or months later to follow up and ensure the family are working towards meeting those outcomes. Perhaps this kind of arrangement would be helpful to you.