I found that your commentary was great. You didn't have any silent spots, and you actively kept your audience connected, but the quality killed it for me. I'm aware you addressed it in your post, but you have to get a capture card if you plan on growing more as you can only reach such an audience with recording your tv. You could always use the emulator dolphin on PC to emulate the game, or buy a standard def cap card. Secondly is mic quality. It wasn't too bad, but I would suggest a relatively cheap headset like Microsoft LifeChat LX-6000($40) if your looking for one on a budget. Lastly If I were you I would talk during the cutscenes, but just not as much so the viewer can still enjoy your commentary along with it.
(This is assuming you're on a budget, obviously there are better options out there, but at a bigger price range) Mic: http://www.amazon.com/Microsoft-LifeChat-LX-6000-for-Business/dp/B00465UNYI/ref=sr_1_2?ie=UTF8&qid=1441896777&sr=8-2&keywords=microsoft+headset
If you can get your office to set your phone up for VOIP, you can keep your office number and use it on your computer. (I'm on a mac, but use http://www.counterpath.com/x-lite-download/ and it works flawlessly.)
BTW, for a headset, i love this: http://www.amazon.com/gp/product/B00465UNYI?tag=thewire06-20&linkCode=as2
Reviewed by wirecutter: http://thewirecutter.com/reviews/best-usb-office-headset/
Good luck!