Login page co-opted and host claims its 3rd party installation

I installed WordPress on my Website (www.financialiteracy.us) maybe eight years ago and have upgraded it a couple of times since. I don’t remember the version; but know that I installed it using Earthlink’s installer. It’s been at least three or more years since I upgraded or updated it. In fact, I haven’t done very much but look in on my site for some time.
Now I want to go back in and resurrect it. It’s been slammed with spam; and I just got a notice from Google that it’s been under some kind of extraordinary “assault” by people leaving hundreds of comments.
I want to kill the spam, clean up the site; and get back to regular blogging. Unfortunately, whoever has been marauding my site has apparently killed my access to it. I know my password and username; but cannot bring up the wp-login.php page as I used to. (The full address is https://www.financialiteracy.us/wordpress/wp-login.php). What are my options? I can access the Website with my ftp client.

You can still access the old blog at https://www.financialiteracy.us/wordpress.

When I look on the host’s site, the WordPress installer biases out any other access to wordpress; and when I ask Earthlink’s support people for help, they tell me that they can’t help me because I used a third-party installer (which is not so). Help!!!! Any help would be appreciated.