Wow Dean, it sounds like you have a bucket load of potentially unrelated problems. I suspect that I have the same HWH control panel and computer as you.
In the mode that Richard has started (taking it one piece at a time), let's look at some of the issues you raised.
Hose under the dash disconnected and blowing air. This is likely the hose that goes to the vacuum generator used to control the HVAC dampers to change from heat to defrost.
The wiring disconnected/missing near the solenoid blocks is not good. If you need it, I can provide you with wiring locations on my front and rear suspension solenoid blocks if you desire by taking some photos of them and sending them to you.
Air leaking from one of the pressure regulators on the rear block. Make sure that it is a pressure regulator rather than a solenoid. Assuming it is a regulator, they do intentional leak out pressure from time to time BUT if it is leaking all the time that is not right and will likely have to be replaced unless it is leaking around the air line connection. If it is a solenoid, it likely needs replacement. After buying my coach, I had Newell replace all of the leveling solenoids as a precaution.
Air leaking from under the left front as well - this could be a right front or left front lowering solenoid stuck open and causing air to discharge (likely the left front since you mentioned that the left side was down).
No response to any input to the panel. The sensors in this panel send electric signals to the control box. On mine, that is located in the bay behind the right front tire. It could be a lack of power to the control box or a bad connection between the keypad and the control box.
Just keep things simple and address them one at a time. Each corner has two solenoids. One raises and one lowers the air bags that location. These are normally closed. Electric current from the control box opens either the raise or lower solenoid to let air into or out of the affected air bags. The control box does the work directed by the touch pad. If the control box does not have power or the electrical cable between the touch pad and the control box is not connected nothing will happen.
The first thing I would check would be the connectors on the rear of the touch pad to make sure they are making a good connection. If it still doesn't have lights coming on when the Level button is touched then I would check the fuses to the level system. On my coach, that is fuse 2 on the chassis fuse panel in front of the passengers feet (red wire), fuse 7 (yellow wire), fuse 14 (brown wire) and fuse 18 (orange w/1 black stripe).
I don't know what type of vandalization took place but if the dash was damaged, the connections to the touch pad could be off or damaged.
Installed a T with a schrader valve to air up the left rear so it wouldn't rub. The HWH system uses two sets of inputs and two sets of outputs. In leveling mode, the solenoids I have been discussing go to work based on a level sensor typically located in the bay near the center of the coach. In travel mode, ride height sensors on each side of the rear axle and in the center of the front axle determine if air should be added to or released from each set of airbags. There are a set of travel solenoids in the front and in the back that are next to the leveling solenoids. If those are not getting any signal from the control box, they will not raise/lower the appropriate corners of the coach. One way to test this is to apply power to the hot side of each solenoid with the engine running and see which side goes up/down. Incidentally, the inside of the control box has dozens of fuses.
I am certain that Newell can give you more details on the wiring to the various solenoids BUT until you get power to the touch pad, nothing is going to work correctly.
I like this
HWH manual.