1. you owning a domain, e.g. familyname.potato , does not prevent you from owning 10 other domains. How you chose to use each is up to you. With whom you share each also.
2. which services? I don’t understand. I typically use e.g. ProtonMail on my domain but I can have for each a different mail provider. I don’t see what somebody knowing which service uses is a problem as long as that service is secure.
3. I’ve been using my own domain for years, maybe a decade now (can’t recall tbh) and had 0 problems, including with banking and public administration. Nobody knows even what it is or who owns what, just that it works.
4. no idea, I know I’d use a free ProtonMail account if I needed sth disconnected from everything else
5. your CV should be something public anyway, you’re trying to prove your are somebody with skills they can trust. If you have problems linking your skills with your identity something feels off. I have 0 problem saying I can do some locking picking publicly. Anyway your CV is also a temporary document. If somebody doesn’t visit your domain the moment they open your CV, chances are that years later it’s entirely irrelevant.
6. yes, I have multiple domains because I don’t have to have 1 identity. I can share only professional things with you and personal things with others, or vice versa. Having different domains, and subdomains, for that help me doing so.

1 Is there anyway to use a FirstNameLastName domain for registering for services without doxxing myself while still receiving the benefit of a custom domain?

Yes, either use someone else’s name or make one up.

2 What is the best structure for creating emails for services? For example I’m currently using <ServiceName>@CDexample.com but the downside of this is if someone knows your domain they can effectively figure out what services you use and this possibly could be used for osint and doxx you.

Yes but it’s unlikely. You can’t (typically) get a list of addresses from a mail server.

3 Should I use my custom domain for Banking and other financial related services?

Personal preference.

4 Is there any point to use a service like addy.io with with a single custom domain?

Personal preference.

5 If i use my custom domain on my cv would my whole domain forever be correlated with my other personal data on my cv and sold to data brokers?

Yes, but this is probably low-consequence, at least for the near future.

6 Is there any point to own more than one domain?

Yes.

Frongt’s answer is great. Another couple of thoughts:

For the domain name, do you want firstlast.com specifically, or could something close work (maybe you already have it and there’s no more choice to be made)? I opted for a derivative of my name in order to keep it professional and for it to not become outdated. If you’re Taylor Robin Smith, would something like tarsm.com work? Without already knowing your name, it appears random. Any service that could reasonably make the connection probably already has your name anyway.

One side note: when choosing your TLD, I suggest one of the “classic” ones – .com, .net, or a country. I’ve run across some forms where the email validator rejects the newer ones like .works. Not a lot, but even one is inconvenient.

For the service naming, I do like you suggested for the name, but I just use a catchall. There’s no address actually created, my mail host just sends anything to my main mailbox – [email protected] receives [email protected], [email protected], or [email protected]. To my knowledge, the only way to tell I actually use a given address is to check my inbox.

I personally use a service like addy for less personal things, e.g. signing up for an account on a forum, signing up to newsletters, etc.

I use a custom domain with a catchall inbox for things I may need to contact someone over, or need a sense of legitimacy, e.g. buying something online, online account with doctor/insurance/government/etc, I give every service a slightly different email address so I can always tell where someone got it from (or who sold my data).

And one that I share with a limited set of friends and family.

I don’t see why you’d need a firstnamelastname.com domain, just find a common domain tld (com, net, etc) and buy something short and easily pronounceable or spellable in the off chance you have to give an email address IRL. When you want to put an email on a CV, use [email protected], that’s just as professional so long as your domain isn’t balls.com or something.

2 What is the best structure for creating emails for services? For example I’m currently using <ServiceName>@CDexample.com

That’s more-or-less how I use Fastmail’s catchall/wildcard alias feature.

but the downside of this is if someone knows your domain they can effectively figure out what services you use and this possibly could be used for osint and doxx you.

How would someone know that what services you use based on that? To do that they would need to know what email addresses you’ve actually created/used. In any case, you could salt each local-part so it can’t be trivially guessed.

3 Should I use my custom domain for Banking and other financial related services?

I use mine for nearly everything.

5 If i use my custom domain on my cv would my whole domain forever be correlated with my other personal data on my cv and sold to data brokers?

Perhaps. When I want an extra layer of anonymity, I use a Fastmail’s masked email that’s not associated with my domain.