One thing to consider with the site…even if you get to keep your content there are going to be cached copies of posts that people looted and your new site starting from scratch will not have as much link popularity as this one built up throughout its history, at least not off the start anyway.

Rather than switching domains I would see if you could just get Scrivs to let you keep the domain and pull whatever posts he made.

If he is unwilling to do that, make sure he at least 301 redirects this domain to your site until whatever point in time he decides to resurrect this site again. Given my limited understanding of the working relationship I feel he owes you this, and this will help your new site build off the authority you have established here.

301 redirects are pretty easy to do. There are many examples of how to do them posted across the web. Just make sure you save a backup of your old .htaccess file before changing it.