Which brings us back to the question: how does he get around the little inconvenience of marriage being a Sacrament?
I agee that it is a very real question. We don’t know how is he going to “get around” that.
He may give up on trying to legitimize his current civil marriage, separate from the civil spouse and become celibate.
Or
He may succeed in annuling both prior marriages, and if his present civil spouse had any on her own, she might likewise succeed annuling those, at which time they are free to regularize their civil marriage as Catholics.
It is a standing joke how, supposedly, annulments are granted to prominent people easily. No one really knows since the proceedings are private. However, given the present serial marriage, easy divorce and plentiful contraception, the fact is that very many marriages are on shaky sacramental ground. Lack of committment to a lifelong, mutually faithful, oriented to parenthood marriage is not that uncommon; quick trial marriages that end barely after they are consummated are also frequent. Imagine that one spouse insisted on contraception and left no offspring; imagine the other spouse had been previously married for whole one month right out of high school, and bingo, both marriages are invalid, one for lack of fruitfullness, another by impediment of prior bond.
What makes marriage a sacrament is the three of you (you, spouse, and God) all completely committed to the union. If you or your spouse entered into the union with serious mental/emotional/spiritual issues, God may not have united Himself with you in your marriage. He cannot be part of something deeply flawed. That is why people can get Catholic marriages annulled. The Church studies the marriage and determines there were deep flaws in the commitment of either party. God would not have been united in the sacrament of marriage with such a couple. So, it wasn’t a sacramental marriage.
You have to take it on a case by case basis. If someone is deeply dishonest about who he is or what he believes, commits adultery, or has personality disorders, then he can’t possibly make a real commitment to someone. If he can’t make a real commitment, God wouldn’t participate in uniting an innocent person to him. The couple would have had a valid, legal marriage but not the sacrament of Marriage.
That’s my understanding.