I don't think Fred Franz was confused, just too close to the material. He was relating the mustard seed to the weeds that Satan planted in the field. Only in the case of the mustard tree there is no dualistic comparison, unlike the dragnet, the field of wheat and weeds, the flock with sheep and goats, etc.
Without the contrast of good and bad, though, the parable about the loaves and the mustard tree are awkward in association with Christ comparing it to the kingdom.
I think Christ's focus was that it would start very, very small, just as leaven is very little but can leaven the entire loaf. Likewise, the kingdom would start very, very small, with one man and then eventually become a huge entity where many birds would find lodging. This can also represent the kingdom in relation to an individual. How it starts with something very small and then it grows and grows into a huge, strong faith. "He who is faithful in little is faithful in much."
As far as the understanding of the other parables, the WTS is so clueless I don't even want to bother explakning what the true applications are beyond noting, as we can see, they don't make all that much sense. Franz was too anti-Catholic anti-Christendom oriented. You can't apply everything to Christendom vs JW scenario.