The eggplant has a perfect flower. That means it will pollinate itself. It does not need another plant. Like many plants with perfect flowers, they don't even need insects to pollinate them. The wind will take care of that. If you plant yours where there is little or no wind, you can tap or gently shake the plant to help pollination.
Another cause for the flowers not setting fruit can be lack of water. The roots are fairly deep, so they need a deep watering instead of just getting the surface wet. Mulch can help keep it moist.
I'm not sure about this one. I think they may be like tomatoes in that if the nights don't cool to a certain temperature, the fruit will not set. That's why I could not grow tomatoes in the New Orleans area in the heat of summer but I can year around up here. I think eggplant is the same way. Your nights may be too hot in the heat of summer. I still would have expected yours to have set some fruit after it started to cool off since your plants looked good. You may have gotten them out too late for them to set fruit before the really hot weather hit. Like I said though. I'm not sure about this one.
I hate to pull my tomatoes, peppers and eggplants until the frost hits. The eternal optimist, I guess. I doubt yours will produce anything at the temperatures you mentioned. I'm not familiar with your climate but suspect it will get pretty cold soon.
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