You may wish to rethink this. Both the NABRE and http://biblelexicon.org/jeremiah/3-14.htm says master, not husband. Whatever translation you are using has this wrong.
BTW you can't be a bigamist if one has died . That is why he came in the flesh and died .
Are you saying that the nation of Israel died when Christ did? Or are you saying that since Christ died and Resurrected, he effectively divorced Israel and married the Church? Neither one makes sense.
You may to revisit the term 'grafted in'.
Jer 3:8 And I saw, when for all the causes whereby backsliding Israel committed adultery I had put her away, and given her a bill of divorce; yet her treacherous sister Judah feared not, but went and played the harlot also.