Not necessarily, factors in custody disputes typically look to the best interests of the child(ren), the relationship/bond the parent has with the child and how much the parent has been actively involved in the child's life among other factors of course.
You should seek the legal aid services in your county for pro bono or low cost representation and there may also be a county service program in your area that provides free or low cost family law representation.
It has to be proven that you violated the conditions of your probation and you are entitled to a probation violation hearing if there are allegations against you for violating a term of your probation.
The one he feels most comfortable with and feels that the attorney can devote the time and attention to his case. A separate issue he will have to address is CACI registry or Child Abuse Central Index which is a separate administrative hearing involving your son being placed on this list for abuse of a child anytime there are child abuse allegations, which could hurt/harm his future for the next 10 years.