The Distrtict Attorney is correct in not talking to him. However, it is not up to the District Attorney whether your son in law receives a court appointed attorney. It is up to the court whether he qualifies for a court appointed attorney. There are several factors that the court will consider on the date he is scheduled to appear before determining if he is indigent and entitled to the appointment of an attorney.
Find an experienced criminal attorney! Obviously, if no criminal lawyer wants the case it tells me that the DA's office in that county must be difficult to deal with.
You hare going to have to look around.
Just because you made your son-in-law's bond does not mean he does not qualify for an appointed attorney. The question is whether the accused is indigent - does he have money and/or property he can sell. Some judges get confused on this.
Given the potential consequences of such a charge and your experiences with the local lawyers, I would hire an outside lawyer who is not afraid of a fight.
Not every injury is caused by someone else - things happen. It is nice that you are giving your son-in-law support as you would more than likely know if he is abusive.
You may need an expert to look at the x-rays and testify (or give a report) of his/her opinion on how the break occurred.