I can't comment on co2 because I have never tried it but you can get away with much higher temps than people make out. People act as if your plants will die of temps get into the 30s.
Indeed keep them in the sweet spot if you can but for some (me) it's not possible.
I grow in a tin garage. Ambient temp in summer in my shed was 60c most afternoons when i went in to water the plants. I draw air into the tents from outside of the shed and that kept temps in the tents down to about 35-40 on the hotter days. I have grown through 2 summers now and i can tell you my plants don't miss a beat in the heat.
I must admit though I do try and time so I'm not harvesting in the heat. Nothing worse than a snap dried harvest
Absolutely you can grow in high temps. I did similar to you for years through QLD summers without co2 or environment controls. Probably some of the best learning I had on indoors in relation to heat, Rh, EC levels, HPS light distance off the canopy and feeding schedules. Not to mention trying to keep a healthy root system in F&D at the same time.
I think old mates trying to have a controlled environment.
Btw, went and had a splurge the other day.
