With his history, a re-purposed room on death row would be the most likely place for them to keep him. In New Hampshire, as we only have one inmate on death row, it's actually part of the maximum security facility, or as it is more commonly called, SHU (Secure Housing Unit).
Getting into prison is complicated enough, but let me describe what you go through to get into SHU. You approach the Alice in Wonderland gate. It has this name became it is all secret. A voice asks what you want, and you explain. If the voice deems you worthy, the gate silently opens. No human is in sight. You then proceed to the next gate (no options on where to go), which is next to a guard tower. The guard lowers a bucket and you place everything you have into it. The guard looks at it, and then returns a pen and legal files. There's very little you can bring to SHU.
The guard opens the second gate and you approach the actual building. The door silently opens and you enter a small room. There the guard has you fill out a form and takes a wand to see whether you have anything metal on it. The guard then escorts you to a small elevator that takes you to the second floor. There a new guard meets you, and gives you a pat down search. You're then escorted into the phone room, with the glass partition, and locked into a small room to meet with the inmate. Inmate may be cuffed and shackled.
In other words, getting into prison isn't much easier than getting out. Maximum security is what the name says. Guided tours do not go into SHU. SHU is a major step above normal visiting that is impressive in what you have to go through.
Rather than your plan to break into prison, I'd have the friendly guard inject him with something that causes a problem requiring him to be sent to the hospital. An epi-pen or two could give some interesting results.
Prison guards do not have sidearms. Nor do they normally carry nightsticks. Shotguns and rifles are used, but only by guards who are not having one-on-one contact with the inmates.
As a death row inmate, he would only move out of his cell in cuffs and shackles. He would stick his hands through the door of his cell while facing away to be cuffed There's a slot in the door. He would then go the the far side of his cell while they open it, and then his legs would be shackled.
Best of luck,
Jim Clark-Dawe