What are our options for being assaulted on a job?

He can't sue the employer for being terminated, unless he had a written employment contract which they violated. Unfortunately, when there is no employment contract, you are an "employee at will" and may be fired at any time, for any reason, even such a blatantly unfair one.
He can appeal the denial of unemployment and attempt to show that his termination was not "for cause"--that is, he was not insubordinate, did not violate employer instructions, was not absent without authorization or a valid reason, etc. Only if he was terminated "for cause" should they deny him unemployment. He can initially appeal within the unemployment office (they have an appeals process) and, if that doesn't work, could file a legal action to further appeal in court.
The employer is not obligated to pay for his hospital visit unless the employer was at fault (see below), so they can look to recover this cost from your husband. It was his medical visit and is his responsibility, unless there was fault.
He can sue the coworker who attacked him for the medical bills and lost income from losing his job (a court might not give him the lost income claim, because the court *might* conclude that it was not the attacker's fault that the employer fired your husband, but it's definitely worth including the claim in the suit), and possibly also for some small amount for "pain and suffering." A person who intentionally attacks or injures another is liable for the injuries and costs he causes.
 
The employer is not usually or generally at fault for the criminal actions, like assault, of its employees, because committing crimes is in no way part of their job. BUT the employer can be liable (such as for the medical costs) *if* they had some reasonable warning that this coworker was either generally violent/dangerous or else posed a specific threat to your husband (e.g. had made threats to or about your husband, which were brought to the employer's attention). If they had knowledge of specific threats but failed to take reasonable action (anything from changing the attacker's or your husband's duties or shifts so as to separate them, up to terminating a dangerous coworker), that could make them liable under the theory of "negligent supervision." If they are liable, then in that case, your husband could likely sue for improper termination, too, since even with employment at will, it is wrongful to terminate someone for the employer's negligent act.