Good job for deciding to do your research. Breeding bettas is NOT easy and if your breeding solely to sell you have an even harder road because
1. long fin males can take up to 6 months to fully mature and look "nice", this is especially true for male VT.
2. most stores do not want stunted fish (which is usually what happens in your first few spawns)
Also remember the amount the petstore is going to give you for your fish probably won't even cover the costs of breeding, not to mention the time involved.
I also agree with your temperature situation. Your temps should remain at a stable 77-80* all the time. For spawning you really should have the temperature at around 82-84* IMO. Constant temperature fluctuations can adversely affect the health of your fish (which in turn can affect they're spawning abilities).