Well, not sure why it needs 6 tickets though, that might indeed have slowed down things, respectively cost your tickets some spots in the support queue.
I’d choose the category that covers the worst thing/s (that would be ToS violation for both threatening to take down your site, and demanding direct payment, and whatever else the seller may have done that’s against Tos; that doesn’t need a separate report for every separate ToS violation IMO, should be far better if that’s all under the same ticket, so the same agent can see everything at one glance), and since it’s about the same order # and seller, I’d put all the “minor things” like wanting to cancel and be refunded in there as well, so the same person will look into it and treat it as “one case”, which it is, after all, even if there are different aspects.
I’d assume that ToS violations category has more priority in the support queue too, so it would make sense to use that for your case, especially as the “threatened to take down my site and I freaked out” bit is urgent (but, yes, that’s not something Fiverr can actively do anything against, you should change your password, so the seller won’t have access, for a bit more peace of mind, and Fiverr can take action on their part by suspending the seller).
Personally, I’d close all not so relevant tickets myself now, if any are still open, and just use the most relevant one, and update that 1 ticket with other relevant info regarding that same order and seller that may be spread over the other tickets, so they have anything of importance, and anything you want from them in the same place.
Then, you can either be patient (but remember to change your site’s password if you haven’t yet!), or you can try what apparently some people do, send a direct email to support with the ticket number (the one of the remaining 1 ticket), or tweet them and ask them to look into your case because it’s urgent. I don’t know in how far that will help, because probably everyone says it’s urgent, but probably not everyone contacts them outside of the ticket system, so maybe it can speed things up a little.
A calm tone and an as precise but as short as possible account of things, while not leaving out anything important, and attaching any relevant “proof” (screenshots) should help.