Answer:
I can be swallowed, but I can also swallow you. What am I?
If a man carries my burden they will get crushed to death. Though not rich I leave silver in my track.
A young man wants to have me but when he has me he no longer wants me. Blade in hand he attacks me and does his best to remove me. Yet he knows that it is all in vain.
I am heavy forward but backward I'm not.
I am a king who's good at measuring stuff.
Pirates put their booty in it.