The reason you are getting 45 amps is you are erroneously trying to work this out as if it was an unregulated setup using only ohms law. That just isn't how it's done with regulated devices. 320 watts is
85 amps to start, this
increases as the batteries discharge.
Read this article to which clearly explains how I'm getting to these numbers. Then model it yourself in steam-engine and you will see. I also wrote this article on the subject. The fundamental thing to understand is that in a regulated device the batteries are connected to the regulator, NOT to the coils.
The way amp draw works on a regulated device is
not intuitive and many people get it wrong. It took me a while to get head around it after using mechs.
I'm not trying to brow beat you, I'm just interested in helping you. Also this is a public forum so it's imperative that correct information made available.
In answer to your question, yes I think these 300 watts devices are an accident waiting to happen. Just look at yourself, you seem reasonably experienced, but you got the maths wrong.
Manufacturers know damn well they are pushing the boundaries with these devices, but also they know that bigger and bigger numbers is what sells. Anyone who has been vaping for a few years knows that you don't need a fraction of those power levels to produce massive plumes of vapor if that's your thing.