I doubt a therapist will ever tell you to keep the father away unless there’s a court order, abuse, etc. It may be better for their overall health but without a court order they can get in trouble for telling you to do so without evidence. I would start documenting the inconsistencies and deadbeat behaviors, get a consultation with a lawyer, and bring it to court.
As a medical professional I don't think thry are allowed to take sides. You might need to lawyer up to get specific information that you need.
When you say therapist…. what do you mean? Do you mean counsellor? Do you mean Counselling Psychologist, do you mean Clinical Psychologist. Regardless, they aren’t going to tell you what to do. If you want clear advice on that, the professional to speak to would be a family lawyer.
I don't think that therapists can tell you to keep the father away. They are there to help you figure things out, not tell you exactly what to do.