How can an old Facebook page containing inappropriate posts and shares be deleted, given that the account is suspended and inaccessible due to not knowing the password or email, and does this entail ongoing sin?

As long as you have exerted your utmost effort to remove the reprehensible things you propagated but were unable to do so, their persistence will not harm you, nor will their sin befall you. This is because whoever repents from disseminating something forbidden has their repentance accepted, and they are not harmed by the lingering effect of their sin if they are unable to remove it. Indeed, repentance erases what came before it, and one who repents from sin is like one who has no sin.