Your question on verses 66-67 is answered by verses 64-65:
“64 But there are some of you who do not believe.” (For Jesus knew from the beginning who those were who did not believe, and who it was who would betray him.) 65 And he said, “This is why I told you that no one can come to me unless it is granted him by the Father.”
Not all his ‘disciples’ had been given him by the Father, for some of them did not believe.
He didn’t want them back - they were not his in the first place.
because He knew they would refuse to believe Him regarding His teaching of His body and blood, among other things.