You say that you're "tagging the absolute s**t out of every video with everything under the sun you can think of", so I decided just to check your latest video to see the SEO metadata:
1) There is no description. It's literally just the standard boilerplate "Please like, subscribe, and comment".
2) Title is not optimized. You're optimizing for "StarFoxZero" (as one word), when I'm guessing the game's title is not just one word. youtube will autocorrect a search for "starfoxzero" to "star fox zero," in which case your title is not a direct match...as a result, all things being equal in terms of analytic data (although, keep in mind...it's not), youtube would prefer a title with "Star Fox Zero" which is an exact match, over "starfoxzero" which is an indirect match.
But even more, the title of any game is not optimal...it's very generic. You need to say more about what this is. Is it a review? Is it a strategy guide? Is it a fan based parody? You might think to yourself: "well, it's obviously episode 5 of a let's play"...but youtube doesn't KNOW that if you don't put that in your metadata (title, tags, descriptions).
But even worse...you've got to consider your niche. In this case, "Game Title" is not optimized...there are too many videos using that. But even "Game Title Let's Play episode number" is likely to be saturated with a lot of different videos. I ultimately can't decide what content you want to produce, but if you're going to compete with something that a lot of other people are doing, then that's going to be more difficult than trying to do something different.
3) Tags are not optimized. You have a lot of single word tags like "grumps" and "game", which youtube will interpret as if you're reaching people searching for those single words. But even if you meant to type "game grumps" instead of "game" and "grumps"...that's not what your content is about. (you do have a tag for "gamegrumps" all as one word though, but still...that's not what your content is about.) You do have a tag for "star fox zero", but again, you have no tags for what the video is: "star fox zero let's play" or "star fox zero gameplay" or whatever. So you're competing not just with every other star fox zero let's player, but every person making a star fox zero video *at all*.
All of the stuff above is before anyone has ever seen anything in your video. But if you don't have the basics of metadata down, then I don't see how you think people are going to find your video. Yeah, you can try posting it on websites and social media, but if you don't have organic traffic through search, then that's going to be a very manual process to try to get traffic.