That is a fine unit there. I have a 1969 Zenith ready for sale, almost finished except for the record changer doing what yours does, sometimes
One of the capacitors that couples the push-pull output transistors to the speaker is likely partially open.
This is a common problem with solid state amps. These also have a main/remote speaker switch and even a headphone jack that may need cleaned.
That is a common prblem with the record changer. There is a long, flat actuating rod that may have the one end bent. There is a good tutorial on how these changers work in Sams set 767. It is a good idea to lube these exactly as directed. I saved a few RCs over the years and Voice Of Music, which supplied them to Zenith, changed little so parts will swap.
The lid problem is easy, there is a screw on the bottom of the spring box that needs tightening. I just fixed a 1964 Admiral this way.
BTW, Kitty may be trying to help you on this one. A certain Ted Nugent album might motivate him/her.