Sorry I must have missed your questions, if it wasn't Visvanath pointing to this forum from other post, I would have missed it completely.
1: Fine, you can do that, using WordPress as landing page, but for your understanding, the level of SEO that WordPress will give for one page, Moodle may be able to give you even better than that.
2: Once page loaded at user's end, the API loads from its respective servers, so if you have embedded YouTube, FaceBook etc, it will be their servers serving the content, without even effecting your Moodle...........but not to mention, using YouTube will take away the professionalism from your courses being a free service. Current streaming technologies (popular ones) will allow use of HTTP protocol, and no other method required, so even your current BlueHost server will be good enough to send video to user. But YouTube has its own charms (ABR, 4 qualities, and so on)
3: I am not sure I grab this question correctly, elaborate a bit further, unless Visvanath or Mary has already answered.
4: Blogger actually Boosts SEO, based on the URL's that are used in blogs (containing the title of the page in URL), that is one of the important factors in SEO ranking,s, and I had recommended blogger to be used as a blog for its Google's product and Google puts its products at high rank without you doing anything about it must as when compared to WordPress.