Interesting.
I tried to find the blog you mentioned, and sadly it has indeed pretty much fallen off the end of the internet. Neither the Web Archive nor Google's cache has it, sadly.
But I did find proof it once existed: https://www.sexchatsexchat.com/peeps/sexystuff/tag/sexy-quot...
I also found an archived registration record from 2014 for http://cn.sitexy.com/whois/sexchaterotic.com but I'm unsure if this was relevant.
I've sadly seen quite a few tumblrs be destroyed, in the form of users who I suddenly realize have a "2" or "-new" after their name. The content they're posting is sufficiently interesting to their followers that they get their network back reasonably quickly (one person finds the new account, follows them, then that spreads the posts back into the rest of the network), but they lose the link between the notes/reblogs and their ID.
And that's the thing. From the standpoint of "normal" social networking, having new people discover you, etc, you generally do want to keep your identity so people can track that you're you.
I guess for real fringe interests (although I can't really say what you're posting is that much of a fringe interest, at the end of the day, really...), Tumblr doesn't seem the best place to go - which _is_ pretty hypocritical, I'll give it that, yeah.
I can't find it now (agh) but I remember reading an interesting Yahoo report that said something to the effect of shutting down Tumblr. All I can find now about it is earnings reports, but this PDF was a bit more explicit about it than that. Tumblr will, eventually, one day be gone; and the world is going to be a very very strange place when that happens. :/
There's no point stressing out about that point now though; nobody knows how it will pan out - maybe some crazy-insane (in a very good way) bunch of people will band together to make their own new thing, or maybe everyone will converge on some existing site. I doubt _everyone_ will disperse, although that will sadly happen. IMO, any individual effort will be fruitless unless it fits in with the group dynamics that play out at the time, and I see no point in taking the chance that the frantic freakout efforts I make will hit that dynamic, so I'm just watching.
This being said, I definitely classify the question of archiving as something that is a very good idea to do right now, IMO. Sadly it seems so unnecessarily nontrivial to do so; I'm not aware of any software to download tumblr accounts that isn't a completely broken half-an-hours-effort-at-4AM job. This is sadly probably why there are few/no backups of more rare accounts. :(
It's possible the Web Archive might have something, but the few parts of their archives that are public are effectively impossible to search (you basically have to download GBs if not TBs of data, open it, go "nope", delete it all, and download the next set).
Hm, this turned into a bit of a rambling rant.
I'm really glad you were able to export the content into wordpress (was it the one I found above? lol). Is the WP installation hosted by you? That, along with picking a smaller hosting provider, and verifying ahead of time that they're fine with the content you want to post, should hopefully minimize heartache. (This is actually a general protip: go with a smaller provider who's one or two people, let them know what sorts of DMCA/takedown/angry emails they might get at your behest and how you plan to deal with them, and even crazy content (eg, obscure political views, flamewars on steroids, sex chat-related sites, etc etc) will stand a chance at staying up for a little while.)
Actually that makes me think of something.
The thing with hosting your own website is that, unless you operate, say, Sci-Hub, which has the kinds of enemies that can pressure domain registrars into deregistering you, you'll be fine, because, in the scenario where your hosting provider boots you (or gets yanked in the middle of the night themselves - this can sometimes happen with tiny outfits), you just switch providers, apologize for the downtime :), and move on. (Obviously you have a local site backup. Right?) DNS registration is a bit hazier thanks to reregistration bots that constantly sniff for expiring domains and snatch them. Some of the automated systems that do this will even pay $$$ to grab the domain early in the termination pipeline (expiring domains go to auction before they are fully un-registered) if they detect the site was popular.
It may be worth asking around Web hosting communities for a good registrar that doesn't boot fringe interest groups (there are fewer smaller registrars, so the hosting thing I mentioned about going with a smaller outfit can't apply here). I mean to do this but haven't yet.
So... an interesting ideal could be, you could register your blog with tumblr _on a custom domain_, do whatever customization you wanted, post whatever you wanted, and then, when tumblr yanks your site,
a) you still have the domain, so you just pivot that over to your own hosting...
b) ...which has all your content on it, either because you were posting it to both, or because you imported your continuous backup of the tumblr account :D
TL;DR, tumblr isn't for "real" fringe stuff, banhammers are both silly and horrible but unavoidable, using your own hosting will zero your chances of getting disappeared.