We downsized, traded off our 3 horse living quarters trailer for a Exsis 2 plus 1 with a small tack room. So we no longer need to have a 1 ton dully.  Can you pull a gooseneck trailer with a 6.5 foot bed truck? Looking at getting a 3/4 ton truck crew cub.  

simple answer is yes

4" set back ball will help but you don't have to have it

Yes you can just have to keep an eye out for how tight you are turning ect. so you don't pop the back window out. 

Great advice about the set back ball.

I pull one with a 6ft bed and I have a tool box in the bed also. 

Before we got our 3/4, I pulled my square-nose gooseneck Exiss trailer with hubbys short box 1/2 ton. Yes, we used the ball extender, which helped tremendously. I was just real careful to watch my back window, but I never had an issue and could actually still turn decently tight.

Yes.