You can usually purchase 10 years up front. But then you should set a reminder for every 3 years or so to keep topping up, or else you'll forget how to even sign into the registrar.

You're right that having a vanity domain for your primary email address isn't for the faint of heart. There isn't any realistic advice for the average person because it's not for the average person.

Not really? You just jump in and fix the domain name. You have 75 days before a lapsed domain is released into general availability.

Sure, you'll likely miss some emails, but otherwise it's safe.