Preventing my amplifier from being fried again and using diodes
I went ahead and looked at your video.

The coil you are using will look pretty much like a short circuit at audio frequencies.  

You are quite simply putting too much of a load on your amplifier.

Diodes will not help.

You need a coil with far more winding on it if you want to continue using an audio amplifier to drive the coil.



I used this calculator to find that a 1 millihenry inductor would have an impedance of about 6 ohms at 1000 hertz.

I then used this calculator to find that for the available cores on that site it would take over 1000 turns of wire on the core to reach 1 millihenry.

I don't know what core you have, but you'll have to do something like the above to figure out how many turns of wire you'll need to get an appropriate impedance from your coil.