1: How do i know if it is rotting or not? Should be pretty obvious shouldn't it?
Yes, it will feel soft when you push a fingernail or sharp object into it and bits will break off easily.
2: The salt, I will soak it for a couple of days, that should be alright shouldn't it?
Fine but no need to soak it. It does not absorb salt so much as have little bits stuck in the nooks and crannies. I hose them off and give them a scrub with a nail brush, using an old toothbrush, if necessary, to get into tight spaces.
3: It was sitting on, And probably used to grow in clay. Will this affect it at all?
Not if you scrub and rinse it well