>I also haven't decided yet whether the block is corroded through
>at the alum/copper interface (causing the buildup on the base
>outside the block)
Its corroded (IMO). Having a aluminum casing, and probably using the innovatek deposit... made of aluminum (if it's the standard one), and not running an anti-corrosion agent was a bit of a gamble. All it needed was the anodized casing to suffer damage to actively start doing nasty things to your system. Using those barbs might have chipped the anodized cover... maybe poly barbs would be a better option.
Here's another one:
the not so better half.
gunk galore.
caved in, real nasty.