A:AnswerUSB is USB, and HDMI is HDMI. Your Firestick has 2 ports, a mini usb for power and an HDMI to connect to the TV. It's normal for the connectors to be snug. Should be that way.
A:AnswerNo, you should be able to use the old audio RCA jacks (red and white cable). But HDMI will provide a clearer signal between the two, offering a better audio experience.