You have the right to appeal. Be sure to serve and file the Notice of Appeal within 30 days of sentencing. I can not access the likelihood of success on appeal without reading the trial transcript or at least hearing about the testimony in more detail.
It depends if you have a serious injury as defined in the Insurance Law. Contact a personal injury lawyer asap and be sure to submit a no-fault claim with your insurance company within 30 days so your medical bills and lost wages get paid.
Generally a criminal defense lawyer requests suppression hearings. Winning is rare but you get much of the paperwork before trial and get to question the police officer about the case so it is a great discovery tool.
I have handled cases like this before... there are 2 possible legal theories. 1) did Riker's have notice that the other inmate had violent propensities? Did your husband complain about him before the attack? Had the person assaulted others before the attack? 2) The second, and harder theory, is that there was insufficient security. Your husband needs to serve a Notice of Claim on the City of New York within 90 days of the incident in order to preserve his right to sue.