You cant sex seeds by the appearance, fem seeds that have been made through self pollination arent that good at representing the mother and you will still get alot of genetic variation.
Its not possible to produce a male clone from a female seed. Whether feminized or regular that turned out to be female.
I have heard of a process where they take the roots off a male plant and splice it with the cuttng off a female, formerly clone only, plant but im not sure how well that works.