Sounds like your handbrake is stuck or rear brake drums are seized. Check out hand barke system and rear brakes.
you dont you bleed and adjust the brakes
bleed your brakes again...there's air in the lines
There is still air in the system.
Check the petal and make sure that the plastic part that touches the brake light switch when the petal is in contact with the brake light switch is still on the petal, if it is missing you will need to replace it, so the petal will make correct contact with the brake light switch.
You need new brakes
Air in the brake lines
Cadillac brake release: All of the Cadillacs that I have had, there is no brake release. When you put the car in drive, the parking brake automatically releases. This is good, since if your brakes ever fail, you can use your emergancy brake like a regular pedal-thats if your emergancy brake is working good. To add to this Cadillac's have a manual release in case the auto fails. Most are at the top right of the emergency brake petal, there's a little lever that pulls forward. That should release it. ( I currently have a 89 that the petal doesn't want to release half the time)
You need to bleed the brakes. Loosen the bleeder valve on one of the calipers and have someone press and hold the brake pedal. Tighten the valve and release the brake pedal. (If you let off of the pedal with the valve loose, air will be drawn into the system and make the problem worse.)
Your brand pads are worn out. Stop driving this car until you can have the pads replaced.
The Brake booster needs replaced
You need to inspect the brake pads/shoes and have the brake system bled. The soft pedal is air in the brake system. The fact that you are hearing air makes me suspect you may have a defective brake booster. Have the power brake booster vacuum diaphragm inspected.
Your brand pads are worn out. Stop driving this car until you can have the pads replaced.