Stupid question, but where is exactly is my website in DreamHost?

I haven’t logged into the back end in a while, maybe over a year.

Today when I logged into DreamHost, then I went to Manage Domains > WebFTP, the interface was different. It used to be AjaxExplorer and now it is Pydio. I thought I would log into that, and then there were the files that I could edit.

Now I can’t log into the Pydio client, my old logins won’t work.

Also, even a more basic question, where exactly are the website files stored and how do I access them?

Pydio was formerly known as AjaxExplorer. It got a new name a few versions ago.

As for the rest of your questions this wiki article seems to answer all of them: