Hi I have a couple issues. I have the same Mac as you. I purchased a capture card which includes HDMI OUT, HDMI IN, USB 3.0, LINE IN, MIC IN, & AUDIO OUT (earphone).
So my setup is HDMI IN (TV) to HDMI OUT (capture card). HDMI OUT (Xbox) to HDMI IN (capture card). USB 3.0 (capture card) to...