What you want to do with tags basically is to use around 5 to 10. If you use more than that, it means that your tags are not relevant. It is also a very cheap way to get views.
A lot of bait/cancer videos have like over 9000 tags. You can type anything in your search bar for Youtube and you may still land on those clickbait even if it is not related at all to what you wanted.
There is a maximum amount of tags which can be labeled for 1 video, it's not like how it used to be many years ago in Youtube.
Only two top most important factors for Youtube videos is COVERAGE and RETAINMENT.
Coverage is making posts in forums, reddit*, imgur*, quora*. **or any dump sites.
Facebook wouldn't work I think. People curate there.
Facebook is not the answers for everything.
I agree with you about FB, I've experienced it myself. I tried to promote my Youtube videos on FB, but to no avail. As for promoting my videos on reddit, imgur and quora, that would be a good idea. However, I've noticed that reddit has so many subreddits that I don't know which one to chose so that I get as much views as possible. I know it's hard, but there is a trick to get those viewers, I just have to learn how.
ORIGINALITY and UNIQUENESS is a subpart of coverage.
RETAINMENT is basically subscriptions + an offsite (blog). Blog is important bc if someone is interested in the topic, he can dwell further.
I think that a blog would be an interesting idea to implement, but I'd rather spend my time on improving my video content than on a blog.
To win over subscribers, you can make something like a mini-series or just (impress /give a lot for his time). People subscribe simply to "track" a Youtuber and not really for anything else.
That's the best idea you've given me now, I appreciate your advice. Thank you very much!