"co-workers, employers, and neighbors"
I agree with all the advice given so far in comments and answers, but felt this deserved some more specific advice around your stated adversaries.
Establishing an alter ego
For your purpose, you don't need an entire false identity, just some anonymity. I would suggest using a free, privacy-focused email service (ProtonMail would probably be a good choice, though there are others). You probably don't need an anonymous phone number unless you intend to deal anonymously with publishers or other business partners you don't trust, and you should avoid voice interactions at all costs anyway.
Obviously, don't make your alter ego's identity linkable to yours. For example, if you spent your 20s drinking red wine and telling everybody that Kafka was the greatest mind of literary history, then don't go naming your alter ego Franz, or Gregor, or Joseph, or Valli, Elli, or Ottla, etc. Likewise, no dead pets or beloved high school teachers that your internet history might reveal. I'd use one of the countless name generators available online for creating RPG characters, or something like that.
Pseudonymous self-publishing isn't really that hard if you aren't concerned about subpoenas or law enforcement investigations. With your new email address you can create a free site (WordPress.com would be fine for this) and video hosting account. To preserve your visitors' anonymity you might choose to avoid YouTube — Dailymotion would be fine, or take your pick.
If it were me I would take some basic precautions while operating my alter ego — for example, I would install a browser separate from the one(s) I currently use to create and sign into those accounts, and perhaps use a VPN while creating and operating them (though really, that's probably overkill, as the adversaries you're concerned about are not going to have those kinds of resources anyway).
Protecting your readers' identities
As noted in other answers, there's only so much you can do here. So long as your book and videos are on a platform which doesn't require anybody to sign in (all those mentioned above would be suitable) that's probably as much as you can reasonably do. If you were really dedicated, and had the time and skills, you could always set up your own server to host everything, configure it to be logless, only accessible through Tor, etc. But that really changes your attack surface, as your own self-administered server is much more likely to be vulnerable to a curious attacker interested in deanonymising you than the above-mentioned widely-used free services. That is, I think, a bad tradeoff.
Maintaining your pseudonymity
As already mentioned by others, there are some simple OPSEC precautions you will need to take. Most importantly, your real identity cannot have any interactions with your pseudonym, at all. "You" have no knowledge nor awareness of the book, site, or author, don't mention it, and don't appear interested if anybody else does.
Use only your alter ego and pseudonymous details when promoting, discussing, or corresponding about the book, videos, or any other detail about the publication. Don't do anything by voice, obviously. If you are concerned about the stylistic analyses described in some answers and comments here, then keep correspondence from your alter ego to an absolute minimum.
Unless you become the target of a dedicated, experienced investigator or hacker, these simple precautions should be more than adequate for your needs. A lot of people self-publish pseudonymously for all sorts of legitimate reasons, and most take less care than is outlined here without real risk.