Gap in the 2nd deck moulding when hooked

I think the "chin" needs to be pulled-off and the frame pin-ox area checked. That looks excessive to me. Dangerous? Most definitely if the frame is cracked or a weld is broken then it's only going to get worse.
There are plenty of posts on this forum as well as others about fifth wheel pin box issues. Just my 2 cents, but I would definitely have it checked. Good luck, Phillip