I've talked to a few of my girlfriends about this stuff at different times in some depth, as well as a few close friends. Although they weren't into guro they were totally fine with it, even slightly into the idea, and it was good to "share my dark side" as you say. If you've told no one that can be difficult to handle, but the solution to that is just to tell someone, even if it's not easy. If people like and trust you, and are open-minded, they may be a lot more chill with this kind of thing than you might expect.

I have yet to run into someone irl who is into this stuff specifically, though I came very close one time—someone I never met who my best friend hooked up with. But I think it's totally reasonable to expect to meet people who are into this irl. It will just take time and initiative and being open with your partners, just like if you were into any other obscure fetish and wanted to find someone else who was into it. You're never going to be on the radar or hear about many though if you aren't open about it with anyone you know to start off.

Also it's not hard to meet people on this site in /rp or even in /dis, or in the IRC, or in the steam group, or in any other guro-related site or page such as rp/chat sites—often people on there are glad to chat rather than rp and are not going to be expecting some high-literate rp'er or something. Gurochan is far from the only place where guro exists.