2- Never ever use the same password for different accounts.
I may kicked against this because you're being hacked because of the shady things you engage doing with your device such as sites visited, files or image downloaded and many other reckless security measures you have failed to maintain, you can use a single password for as may accounts you have as long as it's strong enough with alphanumeric keys combination, using multiple password can get one confused and lost access to any account he had.
3- Writing down your password rather than saving them on your computer is a better idea.
While writing them down, maintain a good privacy practice over it, not onky your password but your wallet keys as well.
6- My browser preference:
What may be good for you may be others dislike, but there's nothing bad with all the categories of browsers you've mentioned.