Oh, gee. The difference between 'bound' and 'binding' might become clearer if different examples are used. These two are both very abstract.
"The man bound the rock to the wall."
"The man is binding the rock to the wall."
In the first sentence, the man affixed the rock to the wall at some point in the past, and it might still be fixed to the wall, depending on what has happened since then.
In the second, the man is actively keeping the rock on the wall. He might be gluing it there, in which case it will stay bound once he lets go, or he might just be holding it there.
In the same way, the contract is actively binding the parties with obligations. The ship was sent to its destination from its home port, and so it is bound for its destination.
As for your other questions...
'Forth' means 'forward'. It means that the contract puts the obligations out into the open.
You can't exchange 'binding' and 'bound' in most cases, and definitely not in this case.
It refers to the on board bill of lading.