<snip!>4 chickens will likely consume 2-2 1/2 c. total for the day...not each, for all the birds. However you feed it, once or twice, that's about how much each adult bird will eat...1/2 c. of feed, be it dry or FF.
The highest temp isn't a factor...it merely ferments more quickly in higher temps, necessitating one to refresh the feed more often due to the scoby running out of available sugars for fermenting if left too long. Most people will batch smaller but more frequent batches in the summer months so as to not reach that point. Can you keep your FF bucket in your coop or run in the summer months, in the shade, where it's not likely to get that hot? I keep mine in my coop in the warm months and it does fine...it gets double shade there and plenty of ventilation, while I also batch it smaller and more frequently so as to keep up with the rapid rate of fermentation in the warmer temps.
Some people in warmer climates wind up keeping it in the cool of basements or garages for the summer.