Lucette's past becomes this when you realize that Hildyr probably didn't stop with simply firing the maid or shooing away the friends her daughter had in the past...
Rod's curse becomes this when you think of what happens should you pursue the other romantic interests instead because he is set to turn into sea foam when Viorica marries elsewhere. Without Lucette to fall in love with him, who will help break his curse before that?
Fortunately Lucette turning 18 and becoming the bearer of the Tenebrarum averts this; she breaks the curses once she does, so he gets to live on all routes.
To add to this: Word of God states that the timelines in each route falls differently, so while Viorica's wedding fell a couple days before Lucette's birthday in Rod's route, it happened after Lucette's birthday in other routes.
Since the subject of Rod's curse is whomever he loves and not Viorica specifically, logic follows that he in fact wasn't fated to die the midnight of her wedding and would die instead the night of Lucette's should she have married someone else. Thus, if Lucette hadn't gotten there fast enough to stop him from killing Viorica, Rod's curse wouldn't have even been broken and Viorica would have died for nothing.
Given that Myrthos seemed to pick up on the romantic nature of their relationship, it's not a stretch to say he was at least somewhat aware of this as a possibility. His aim was perhaps just as much about getting Lucette indebted to him, as it was driving an immovable wedge between her and her friends that connected her to the Marchen.
The witch who cast Rod's curse must have been quite monstrous. Even Karma and Waltz's curses, which were cast in direct revenge towards them didn't condemn them to death if they failed to break them. Made worse by the fact that he would have been only 14 or 15 at the time he made the deal, meaning that this witch sent a pre-teen boy off to his death if he couldn't fall in mutual love fast enough.
Karma's frequent spats with Rumple over the latter's flirting may seem hypocritical when you find out that Karma used to be The Casanova as well. Except that is exactly why it bothers Karma; he sees the obvious parallels to his pre-curse self in Rumple and projects his own past mistakes onto him.
In Rod's bad ending, he makes a point of saying that he was beginning to love Lucette. Not that he loved her, but that he was beginning to. It seems that by having not made all the right decisions for the good ending, Lucette just hasn't quite overtaken Viorica in his heart yet.
A more subtle connection between Fritz's curse and Little Red Riding Hood is the idea of the "wolf" hiding behind something innocuous that "little red" knows and trusts. In the original, it was her grandmother; here, it's her friend and knight of 3 years.
Karma's nickname connects with his backstory thematically; his curse is essentially a punishment, or "karma" for his past flippancy toward the feelings of other people.