Some of my iPad contacts are missing

The two would be completely unrelated. And I get emails every day from some seller or service which I never signed up for. It's the nature of our e-world these days. Unless you provided any information to the email, you just delete it and not worry about it.

They're most often what are called Phishing Scams --> Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support

I can't answer what happened to your contacts, but it does not mean you've been hacked. As I said, unless you've jailbroken your device, it's virtually impossible to be hacked.

Unless you have jailbroken your iPad, it has not been hacked. What does "acting funny" mean?