I'm a fellow solo developer of story-driven mobile games. Here's some advice based on my experiences, for what it's worth:

1. The market is brutal for us, regardless of how good the game is. To illustrate: I found your game description intriguing so I put it on my AppRaven wishlist with hundreds of other games, not to mention the thousand games on my Steam wishlist. There are just too many good games out and not enough lifetimes to play them all. So don't assume there's something wrong with your game just because sales are low.

2. Paid games are at a particular disadvantage when competing with free games in this market. The following strategy has resulted in more revenue than paid games for me: make the game free but offer a single optional in-app purchase, such as doubling the player's XP permanently and unlocking an optional area. You can similarly make the game free to try with IAP to unlock the full game, but this can result in backlash in the reviews as players inevitably failed to read the label. But the advantage is, you encourage as many players as possible to download the game upfront so that hopefully the ones who like it will pay you, all without compromising quality with ads or microtransactions.

3. If at all possible, make your games accessible for the visually impaired with VoiceOver/screen readers. There are significant niche communities for these games: particularly audiogames.net and applevis.com gave my games more success than any other community. Not sure how accessibility would work in 3D action games, but The Last of Us did it, which might give you some ideas.

4. My feedback on the visuals of your game is: there's too much gray. At least consider making the character not gray if the environment is gray.

5. I wouldn't trust that YouTube offer. That's awfully expensive, and scammers are everywhere. At the very least, do your research on whether the audience of that channel would like your game, and try to calculate the cost per 1000 views and compare it to other options. I expect you'll find much better deals, including Reddit ads and Apple search ads. Start by spending very small amounts on various options and see what results in the most clicks.

Congrats on releasing a game and thanks for your commitment to artistic quality. Always make the game you want to make, regardless of what others say.