Alright! Looking pretty exciting. The plants vary in time when showing their sex, but I want to assure you that there is a window (4-5 days to be safe) that you can first identify a male, and pull it without any chances of it pollinating the female. Usually, in reverse of humans, the male shows first and matures first. Just for information sake, in the past I have had the ability to keep a close eye on a male plant and it was a comforting thing to learn that it took a while for the pollen sack to break open even though they were gaining in size and numbers. So no worries with the defining moments in which you control whether you get seedless funky flowers or some productions of an amazing plant in multiplication mode- you have a few days. If you have the urge to take notes and solidify your knowledge, take some close up looks of the 'crotches' of the branches and stalks frequently. In years of experience, and volumes of literaure, the strong, large, agressive fast growing and stoutest plants in comparison to the others, turn out male a majority of the time. I'd guess within the next 2 weeks you will have no doubt, and need to take action pulling.
About the feedings, if you notice progress and under close supervison you are aware of no negative effects of the current feeding regimen, then it is generally accepted to up the ferts in baby steps. from 1/4 to 1/2, that can be considered alot. In hydro, and especially in your situation, it is more acceptable to test the prime of the plant because of the ability to snap the conditions back to shape with additives that counter the changes. I would say, if you can, see the result with 3/8 of the ferts, and move up by an eighth feed each time. If the plant has been doing as well as it looks, it should be in great shape to take some added nutrients. Just resist the urge to over feed, and give the plant time to grow and show you results. Gain experience from noticing constants, rather than modifying a grow so much it would be hard to reproduce.
So far So Good! Keep it up! Peace!!