Why not?

1. By buying a Pixel phone and degoogling it, you are rewarding good behaviour and punishing bad behaviour, corporations need to be trained like dogs.
2. Google is not going anywhere and their primary objective is profit. By buying a Pixel you are signaling to them a viable revenue stream that doesn’t violate people’s privacy.
3. You don’t even need to give money to google directly, you can buy a second hand-one.

I say, vote with your wallet.

Same here too, a 7 Pro.

You absolutely should. With time, the data they have on you will grow outdated, meaning they won’t be able to track an analyze your behaviour because they’ll have no idea how you behave now. It’s like the trail going cold. Hell, just becoming privacy focused already makes it near-impassible to be tracked, and since privacy-aware software doesn’t track, collect, sell or buy your data, what little they have will be much less useful. Also, if you live in the EU, the GDPR gives you a right to request the deletion of all data they have on you, and they must comply. Most other places probably also have laws in place to request the deletion of your data.