If you’re in the US, anyone can set up a business bank account using your own SSN. It’s called sole proprietor. You’d just have to register for an EIN with the IRS. You might have some state procedures too. It’s generally not difficult to do this, especially if having a business ISP account is what you want.

Garmin and Polar take data seriously. I use a polar and don’t mind using their app. They have a setting to delete data after a certain time limit. I have mine set to 2 years.

No clue. I don’t use any consoles or steam.

You could buy a cheap(ish) device dedicated for this purpose that can handle the apps you want. Think of it as a more expensive chromecast.

A separate device can also mean more privacy depending on how you configure it.

My iPhone has a screen mirroring function. If the TV does Bluetooth, you can display your entire screen and play whatever you want.

I think Android must have a similar feature, I’ve seen connection popups for Samsung devices that I denied from my TV.

If you have a non Bluetooth TV, then it won’t work.