Very interested to hear what Pic three is.. I have to same sponge like thing that grows in places that get very little light, I tryed to put some of it where it could get light and it just melts away
That might be the snail... IDK. Why the UGH? Is it a bad snail? I don't know anything about that snail.
As for the sponge. It is a cryptic sponge that tends to grow and spread in established tanks. High flow and low light are the where it likes to live. It will not survive in high light.
By the way, I wouldn't worry too much about that snail shell. It looks to me like it was an empty shell that was part of your substrate (JMHO).
Looks like you found the right snail.
This picture looks like your sponges:
I used to have these in my 125 gallon tank and my 29 gallon biocube when they were running.
Here is another link: Yellow Sponge, Leucetta sp.
It is just called a yellow sponge or Leucetta sp.
Hope this helps
Kevin G. Kramer -What! It said Signature :P