WHY OH WHY DID I LISTEN??? (LONG)

I may just have managed to crash my tank in one fell swoop...

My Setup:

45uk gal
27Kg LR
Chrushed shell Substrate (GOD HOW I WISH I'D NEVER PUT IT IN!)
2 Mushroom Corals
1 Pulse Coral
1 Koko Worm
1 Feather Duster
1 Copperband Butterfly
2 Maron Clowns
1 DEAD Lipstick Tang (ok ok I've taken it out)

This past 2 weeks my Nitrates have been climbing fast. No other reading
are out of spec, nitrites are 0 and Ammonia is .25.

So needless to say I was concerned. I asked the advice of a friend of
mine who has been keeping marine MUCH longer than I and he said I
should consider taking my rock out and cleaning the debris off in a
bucket of salt water and then putting it back in. He said that if I
have rotting debris accumulating in my tank it would get rid and my
levels would drop.

I was skeptical but last night I did it. How STUPID could I have been??
My tank quickly clouded over (from moning the rock and substrate) and
was soon so full of floating particles couldnt even see in it!! My
fish were freaked! I changed as much water as I had (25% ish) and had
to leave it.

This morning my Tang is dead, my clowns are NOT happy and my Butterfly
is breathing out the top of the tank.

Worst thing is I have had to go away for work today and it will be
another 12 hours before I can do any more work on it.

any ideas of what I can do? I think I'll hoover out the substrate over
the next few changes (providing my tank doesn't crash today) and let it
all settle...

any thoughts?

Dan