this prison is your best in my opinion. many of the flaws that Erebus vault had were fixed, well done! although, I have found a way to escape solo:
Enter the prison with a stack of pearls and a milk bucket(if you want to, you can also bring golden apples). When the guard asks you to click the bed, drop your items in the space between the bed and the obsidian above, try to throw it in the corner as best as you can.
In this position, the guard will not be able to see the items, no matter where he looks.
After this go through the kill check, and when you respawn, switch to the 3 key(if you don't have golden apples) this way the guard will not see items in your hand.
Go up the 1-way water elevator and go down the tunnel to the cell bed. What you do now is pearl to the pressure plate Redstone corridor that pushes you into the bubble elevator to the left of the bed, break a piece of Redstone, then sleep in the bed.
You spawn on the pressure plate, but nothing happens, then drink the milk bucket, break the bed and kill yourself by throwing ender pearls into a wall.

Your prisons are very fun to play, I love them! please continue making and improving your prisons,
Thanks, TallTazo