Help getting started

Preamble- I'm new to the fediverse, and I want some help. I'm trying to regain some of my privacy and data sovereignty, and I have recently gotten into self-hosting. I haven't been on social media for over a decade, except for Reddit, and that was mostly as a passive lurker. I just started getting more active on there this past year, and now they've turned me away with their shenanigans. I'm trying to get into federated communications to still have access to useful information while protecting my identity and data.

Goals- I'm thinking that I want to set up my own Lemmy instance, as well as my own xmpp server (like prosody), and switch over to jmp.chat. I also have my own domain.

Concerns- I want to spin up my own services so that I own my data and have greater control over my connections, and possibly have a hub that friends and family can use. However, I also don't want to expose my domain (Why not? I don't know. I'm completely new at this and until I learn more, I'm playing it cautious)

Questions- So, if I spin up my own Lemmy instance, doesn't that expose my domain,since my username will be username@my-domain.com? Is this the same for an xmpp server? One main reason to spin up my own xmpp server is to own my account for xmpp communications. However, can I tie that to my jmp.chat account, or would they need to be separate.

I kind of feel like a boat without an oar at the moment, and I'm not even sure if I'm asking sensical questions, but hopefully there's enough light in my ramblings to give you all a sense of my goals. Any help would be appreciated.

Edit— for those wondering why I don't want to expose my domain: As an example, many people will post their personal information on social media. They think ‘why not? What harm can it do when I talk about my favorite teacher, or the street I grew up on, or my first date? What harm can that do?’ (Not realizing these are common answers to security questions) or ‘Why not talk about my big vacation coming up?’ (Not realizing they’re letting thieves know when their house is going to be vacant) People reveal information about themselves all the time online without a second thought because they can’t personally see the danger. I can’t personally see a problem with using my domain in this way, but I would prefer to check with those more experienced than me before I learn the hard way that I made a bad choice. I do appreciate you all taking your time to contribute your thoughts.