If you can train them, ala LST, or something similar, you could easily get 8 plants 50 cm overall in there, and I would expect at least 15 grams per plant, IF you've truly got "the hang", as you say.
But you can't just let them go vertical, or your yield will be significantly lower.
i don't trust feminized auto flowers seeds but it's up to you.
Based on your other post I'd say your better off just getting ten regular AF's, mainly because their cheaper and you won't have to buy more seeds. For the $50 bucks you spent on that bag you could have bought some Bluestreak or something and wouldn't have to grow those 'Budicles'. IMO that cab your using could double the yield you are getting now in ~ half the time, if you were using some strain of AF. Your days of smoking those hermie bagseed leaves will be over.
No, you never want to put multiple plants in the same pot, especially AF's because a lot of their growth is determined by root space. If you put four in one pot they would all compete for nutes and that is a very bad thing. With AF's your main concern with pots are going to be height because they tend to grow down more than out. So if you could get some taller pots and you will be able to fit maybe six in that box. I'm not sure on the exact dimensions of that cab your using but you should be able to fit 4-6. Which is going to be about the same number of females you'll get. Be sure to keep your best looking male (put it in a window or something) so you don't have to order more seeds.
You can clone them but they take forever to root and if they do their will be a significant cut in yield. That is if you did manage to clone one. Though since they grow so fast you wouldn't have any real benefits from cloning.
Their would also be no point in re-vegging them if you did manage to do that because they really don't have much of a veg cycle in the first place. Doing that would take much to long and you would lose a lot of bud.
ATM the best way to grow an AF is from seed with only one harvest.
As for the male you can really keep it anywhere since they don't need much attention, use it as a house plant, put it under your bed or sink with a small light, make a smaller cab out of cardboard or something. Just suggestions, the point is as long as they have a small amount of light you should be alright. (even 1 or 2 23w CFL's) All you want off of them is their pollen, but you also don't want that in your grow cab unless you want seeds from all your plants.(one pollinated female is all your going to need to be self sustained on seeds.)