Well, there's a lot to cover in what you wrote.
First, it is true that the brominated disinfection by-products are generally more carcinogenic than the chlorinated ones. However, the risks are relatively low in either case so it really comes down to whether you are trying to reduce your total life cancer risks overall starting with the highest risks and working your way down. Odds are you aren't doing that. There are many much higher-risk lifestyle choices. Also keep in mind that when using an ozonator the ozone will oxidize around half or more of the bather waste and reduce disinfection by-products as a result (because there will be less bather waste to react with bromine).
As for bromine staying in the water and chlorine quickly evaporating, that simply is not true and requires proper context to understand where this myth comes from. If there were no Cyanuric Acid (CYA) in the water, then at equivalent bromine and chlorine levels, so where bromine is 2.25 times higher than chlorine (due to molecular weight differences), the chlorine is 6 times more volatile than the bromine so that is the primary source of the myth. However, with CYA in the water at around 30-40 ppm FC, the active chlorine level is around 7 times lower at 104ºF (even lower at lower temperature) so roughly speaking chlorine (with CYA in the water) and bromine outgas at roughly the same rates.
There are other ways that chlorine can get used up and also contribute to the myth. If there is no bather load, then an ozonator increases chlorine usage/consumption because ozone reacts with chlorine. Roughly speaking, an ozonator doubles 24-hour chlorine demand from 25% to 50% FC loss. The actual amount depends on how long the ozonator runs and how powerful the ozonator. If you use the spa every day or two, then the ozonator will cut chlorine demand roughly in half as the ozone will oxidize a good deal of the bather waste so that chlorine doesn't have to.
Also, with an ozonator, the ozone can make more bromine from the bromide bank so that makes it appear that bromine doesn't get used up. And of course, one can have bromine tabs in a floating feeder so that also helps to maintain a bromine level.
So in your situation since you have an ozonator, I would say that chlorine would work for you if you use the spa every day or two, but if you only use it once or twice a week only on weekends, then chlorine will be difficult because ozone will tend to use it up so quickly that you'd have to add it mid-week to try and maintain a chlorine level in the spa. So you can see how an ozonator reduces the amount of chemicals you need to add. When you had a bromine spa, the ozone made more ozone from the bromide bank so helped to maintain a bromine level in between soaks and it oxidizes some of your bather waste after you use the spa so that required less bromine as well. As I noted with chlorine, only high bather load (every day or two soaking) will reduce the amount of chlorine needed. It's not about reducing the background (in between soaks) chlorine or bromine level, but rather the amount that needs to be added to handle (oxidize) the bather waste and for bromine the amount needed to maintain a background level in between soaks.
As for the chlorine level itself, starting out with 1-2 ppm FC at the start of the soak is reasonable, but as was pointed out you need to add enough chlorine after your soak to handle the bather waste. With an ozonator you won't need to add as much. Though there are rough rules-of-thumb for dosing as a function of bather-hours, the real rule is to add whatever is necessary after your soak such that you still have a chlorine residual at the start of your next soak.
