There is an amazing amount of lack of sacramental knowledge here.
Yes, it turns out people may have been worshipping a piece of bread—but in good faith. Probably cut down on sacrilegious communions.
Beyond that, the problems will not require a great deal of legwork.
If one confesses all the grave sins that one has committed since one’s last putative confession, the faux confession will be covered if one was not aware that it was faux. Yes his present parishioners should be notified, but that will suffice
One does not have to be baptized to baptize validly, and with marriage the parties are the ministers of the sacrament—since Trent, a designated official with faculties is required under most circumstances to witness, but that is not a problem.
I’d mostly be concerned about confirmation.
Now, as I understand it, in France in the 18th century this happened and the man went on and had apparently received episcopal ordination. That was a royal mess.
I have not heard of that before. Do you have a source?