Some thoughts for you:
1) Yes. You can use an RTLSDR DVB-T dongle as the receiver. Contact us privately to set up a feed and get the relevant details.
2) Yes. But this is best done on a separate USB drive, not on the primary SD card.
3) No...SD card is more convenient.
4) No reason not to use a Pi3...but the WiFi, while convenient in many cases, uses a tiny antenna that will be mounted inside a case. It will not produce the best coverage results...plus streaming over WiFi will work but will be less reliable than a wired connection.