Wow a lot of life in that rock!!
The shrimp does look a lot like a mantis shrimp from the photos.
The crabs, probably hard to ID. There are so many different types of crabs you can get that unless it is one that is normally sold as an ornamental crab getting an exact id is difficult. Generally I would recommend getting them all out and putting them in the sump or a different system.
The pulsing thing with the tube (assuming that it doesn't move). I cant remember the name but its a harmless filter feeder, got a few of them in my tanks and they come in various colours. If it moves then I dont know what it is.
The thing that retracted was a feather duster (pretty looking one too).
And the last pic is one HUGE bristle worm (harmless but dont touch it, I got tagged by days ago and my hand is still sore and swollen. Teach me not to follow my own advice and wear gloves).
Looks like its coming on well!