Grant him immunity? He’s the guy that needs to be in the electric chair.
Which is why he is taking the fifth.
He already has immunity, the pardon and the 5th amendment basically gives him a blanket immunity.
There is nothing the Congress can do to get him to testify.
At this point, only a state could bring charges against him, the only strategy going forward from the Republicans in Congress is to expedite the release of anything damaging against him and hope to sway public opinion against him.
Since I don’t see jail in his future, the next best thing for an ego maniac like him would be to make him public enemy #1 in the minds of the public.