The metal disk is used as a spacer. Without it, the button will not make contact with the switch inside the phone. Since it is very hard to remove off of the old button (the glue is very strong), I suggest you buy a button set with the spacers pre-installed.
Try unplugging the television, holding power for 30 seconds, then replugging and see if it turns on. If not, a capacitor may be blown on the PSU board, and you would either have to replace the capacitor or the whole board.
The earbuds are made of molded plastic pieces glued together, and attempting to disassemble it would most certainly render the headphones beyond repair. The jack on your phone doesn't seem to be an issue, since part of the earbud is functional. Unfortunately, you will have to buy new earbuds.