He absolutely adores me in every way but he has no respect for you as his partner, as the mother of his dc, or in your own right.
He's compromised your safety, violated your privacy, stolen your identity, and defamed your character by making you out to be a woman of loose morals.
His attitude is apologetic, but how much of that is sorry for what he's done or sorry for getting caught who knows As he's expressed enjoyment of his activities, I suspect the latter.
Regardless of whether he professes to be contrite or not, he needs to make a full and frank disclosure of what else he's been up to without your knowledge or consent.
Has he shown nude photos of you to his friends/colleagues? Has he sent them to the 'readers wives' columns in certain magazines? Has he posted them on other sites? What else has he signed you up for? Is the account you've deactivated the only one?
To protect yourself against the possibility that at some future date he may claim that you joined the dating site of your own volition and conducted the resulting correspondence yourself or were complicit therein, I would suggest that you seek to log these incidents with the police.
Visit your local Regional Police Authority's website, contact the Force Headquarters' and ask to be directed to the unit or officers that specialise in internet crime and related matters as they may be better placed to advise you than your local constabulary.
This may result in your dp getting his collar felt by way of a chat with 'the law' which may be sufficient to make him realise the error of his ways.
Alternatively you could ask him to swear an affidavit detailing his actions and absolving you of any culpability, or to discuss his behaviour in a joint session with Relate or a similar organisation with the proviso that the content of the session is recorded and can be made available to you or to a lawyer acting for you should occasion arise.
Needless to say, what you shouldn't do is accept whatever assurances he may give you to the effect that he's sorry and he won't do it again.
As for the future, that very much depends on whether he can regain your trust after this gross disregard of your feelings and insult to your sensitivities.