“Or refuse the deal...”
It may not matter. They can grant you immunity whether you accept a deal or not, and then you are painted into a corner.
“They can’t put you in jail for taking the 5th.”
No, but they can put you in jail for contempt if you try to invoke the 5th when you already have immunity, since testifying can’t incriminate you.
Until, like Cosby, it does.