It's possibile to change the state of the domains from "dependent Site Management" (because the client was deleted) to "independent Site Management" and relate the domains with the reseller accounts?
No, thats not possible. Clients and resellers are different "objects" in different database tables. A site can never be owned by a reseller directly.
The only solution that I see at the moment is that you try to change the domain of the site and the co-domains to something that is not used on your server, e.g. domain123.tld and then create a new site for the domain under the correct reseller.