Lots of people contributed really good answers, so I don’t have anything valuable to add to their answers. But I wanted to point out for your detailed question, you include what you have done, what is your understanding and what are your shortcomings clearly. As opposed to a lot of posts with vague, detail-challenged narratives, that’s a top notch post.
And the community delivered by giving good answers, so go community!
Also, you didn’t just ghost after the initial post and interacted.with the people who graciously donated their time, so another bonus point there, as well.
I have been using porkbun.com as a domain registrar.
For email hosting, self-hosting is a lot of effort. If you just want the damned thing to work. I’ve heard good things about Fastmail, and personally I’m using migadu.com. it’s $19/year for micro.
Use any imap client, or if you want to keep using what you’re using Gmail and Outlook and Apple mail apps w all support your new personal account over imap as well