Thank you for the reply.
First of all, unfortunately your father took a plea. He can't have that both ways. That is, once a defendant takes a plea, by definition he gives up his right to hearings and trial and to confront witnesses against him and challenge the evidence. So he can't plead guilty to get a more favorable sentence then what he would have gotten if he lost at trial and then turn around and say his lawyer didn't put evidence out there.
If he feels that his lawyer didn't advise him properly or that he was taken off his medication and wasn't thinking right when he chose to take the plea, his remedy would be to have his lawyer file a notice of appeal within 30 days of his sentencing, which he can still do if that time period hasn't expired. His lawyer would file the notice and then the file would be turned over to a free appellate defender.
The medical situation is far more concerning, as he has an absolute right to adequate medical treatment under the 8th amendment to the Constitution. It is considered cruel and unusual punishment for an inmate to be denied necessary medical treatment.
If your father has a condition that requires medical attention, while the prison does not have to provide the same caliber of medical care that he would get on the outside, they cannot turn a blind eye to his problems either. You can get an idea of what courts have found to be deliberate indifference and what sorts of situations constitute a serious medical need here in this PDF, which was put together by the ACLU.
In my experience, outsiders such as family members or well-meaning friends are only going to get the runaround when they try to inquire too closely about what's going on with their incarcerated relatives, particularly when the questions relate to an inmate's treatment -- medical and otherwise -- at the hands of the Department of Corrections.
If your father is still in jail, it takes a lawyer who does civil rights work to break that pattern. They not only can visit an inmate when family and friends cannot but they can get in touch with people in the system who will not speak at all to family/friends and thus have a much better chance of turning the situation around. A lawyer can also file a writ of habeas corpus to get the inmate before the judge and to get emergency medical care ordered.
If your father had a lawyer on his underlying case, that's where you need to start. Contact the lawyer, let him get your dad before the judge and get medical care ordered. You may also want to reach out to the ACLU. They have advocated across this country inmate rights. Even if they have too much on their plate to get involved directly at this time, they may know of others in the vicinity who would offer assistance.
Their national website is at ACLU.org, but the American Civil Liberties Union has branches throughout the country.
If your father is at liberty now, he may have a civil suit based on their neglect of his condition while he was incarcerated. The ACLU would likely know of someone in his area who would be able to assist him with that.