I would not intro this way at all.
You want to "eventually" be a breeder, but since you've had a male and a female together, even for "short periods" you have taken that step past eventually.
People are jumping all over you because you've been a member for over a year, and have less than one post per month you've been on. No one knows you, your chins, or your set up, so all we can really do is assume.
One thing I assumed was that you don't have another cage, because I don't understand why you'd keep putting the female back with the male. I don't know if it's ever worked for anyone, but to me joint play time is a waste of time for intro's. I personally, throw 'em in and see what happens.
If you want to slow intro then I feel the best way to to set two cages by each other with the desired intro chins in them. They each have their own space, but can interact. Once they get used to that, and start spending time by each other, put them together.
ETA: Never mind the advice. I have new advice. Get chins from quality breeders. You have 3 chins, per your status, and you have one male and two females, per you in this thread. You're trying to intro a female to a male you know nothing about, that came from a pet store, and had an unexplained abscess and eye issue. Doesn't sound like you've done much if any research on here in the last year at all. Kits can also fit through the wire on those super pet cages. The benefit of only having one post per month... it's easy for people to see what you've posted...