How do I know if bootloader flash was successful?
See my page about burning bootloaders.
The sketch there has a &quot;verify&quot; option so you can check if the bootloader was burned.
See my post What happens when code is uploaded using the bootloader?.
With Optiboot installed you expect to see three flashes:

As for your other problems, see Have I bricked my Arduino Uno? Problems with uploading to board.
You may well not have set the fuses correctly.