That cylinder is what I guessed it was from your description, old style one way pressure up and gravity down setup. The low pressure line from the rod end was connected to the PTO pump suction and as the cylinder goes up the oil feeds from there through the pump and valve to the piston end of the cylinder. As the hoist is lowered the oil flows back from the piston end through the valve to the upper end of the cylinder in the original system.
I can see in your valve stack you have some sections with a single work port, these would seem to be designed for single acting cylinders. Like I said you can just connect one work port to the piston end of your dump cylinder and the other work port can be teed into a tank return line if you're using a section with two work ports, it will work.
I'm thinking you need to repack that piston on this cylinder, but you might make sure you have pressure on the hose first, you could cap the hose to the butt end of the cylinder and gently engage the hoist valve, you can hear it load up and maybe the relief pop open if the valve is working correctly. You know you have pressure on the line going to the top of the cylinder as you say it blew off?
That's a pretty big cylinder probably designed for a fairly low pressure you might consider adding a relief valve between the valve stack and the cylinder, though I can't advise you on the correct pressure setting. Maybe start at 1,000 psi and if needed work up from there?