Which is why you don’t bother with receiving the Eucharist, right? After all, this whole “faith thing” is purely cerebral, having nothing to do with physical reality. It’s all just a state of mind!
I’m sorry, but yours is a very non-Catholic opinion in this regard.
No, that's not true.
Indeed, faith is in the intellect. Period. End of story. Faith is not in someone's body, and the state of the body can't impede the faith. Nor is it an emotional state.
Physiological state, emotions, etc. can influence (help or hinder) the faith, but they cannot somehow wipe out the faith.
We are not charistmatics who believe that faith is an emotional phenomenon. Physiological and emotional states can have an influence (good or bad) on the higher faculties, but they cannot directly effect any change in them. Period. That is simple Thomistic philosophy of human nature. Ask anyone here who has spent a couple years in seminary.
As for the Holy Eucharist, that's a different thing altogether. When one receives Holy Communion, the Sacrament is an instrumental cause of grace provided that one is properly disposed.
If this priest's soul was effected, it was due to the fact that he consented to the jab by his will. If someone had tied him down and forcibly injected him, that would not have any impact on his faith. Quite possibly on his physiological, psychological, and emotional state ... but not on his faith.