Brave is Chromium-based...it's literally a fork of the core source code for Chrome, so I don't think it would be any more insecure than that. And with Microsoft forking Chromium for Edge, Chromium should continue to get top-notch support on that front.
Ethereum is not a scam. It has evolved a great deal over the past 6 years, and thanks to zero-knowledge proofs, ETH does scale now (up to 2300 transactions a second, without any need for further upgrades...see Loopring for an in-production implementation of this tech https://loopring.org/#/), so you should update your knowledge on the subject.
It's not fake money. It's getting paid to view ads. This is not even a new idea. I used to use an internet service back in the 90s that was free as long as they could spam me with ads (NetZero). Facebook and Google make hundreds of billions of dollars off of ads, do you really think there's no room in that to give back to consumers of ads some portion of the revenue? The only reason they don't is because their duopoly over internet advertising is pretty stable right now.