It sounds like you're saying he would go after MT (the mistress), to hurt Fotis, correct? If that was the subcontractor's intention, then I agree with you, that would hurt Fotis more.
But what I'm actually saying is, that the subcontractor wants Fotis's financial troubles to end or perhaps is very angry that they will not end and that Jennifer's family and their lawsuit and the divorce is to blame. Remember that in the divorce proceedings, Jennifer accused Fotis of hiding money, his assets could have been frozen during this investigation process, and a lot of people who are owed money could be very bitter as a result, creating IMO more likely suspects with greater motive than the husband. If this is the case, we are dealing with a number of people, who have families and obligations, who are just very angry at not being paid, and has chosen to place blame on Jennifer and her family. And perhaps this is an attempt to coerce or intimidate the family into backing down from their lawsuit and letting Fotis recover so he can pay all of these people he owes.