It sounds like you had a lot of butter in the pot and when you reduced the wine to nothing you were left with fat and wine. Reducing wine on it's own is not the best way to go after a great red wine sauce in my experience. You would have to reduce maybe 10 bottles of red wine to get a syrup. I've never tried that, but I think it would work. Or, you could add a lot of gelatin.
Also, you shouldn't have to mess around with xanthan gum to get a nice sauce like this. In the future you only need .25% to get a soup texture.
In most red wine sauce recipes the wine is reduced to concentrate the flavors, not to thicken the sauce. That's why most recipes use a highly gelatinous stock that's reduced to get a "medium nappe" sauce.
So in a very general when I make a red wine sauce, I take two parts wine to one part beef or veal stock. First it reduce the wine with whatever veg I want like mushrooms and carrots. Bring to a boil, flame off the alcohol, and simmer until reduced to one fifth of it's original volume. Meanwhile, I would be reducing my stock to a forth of it's original volume. Add the stock to the wine with any other aromatic you want. Like thyme, pepper and so on. Reduce until it coats the back of a spoon, or test on a plate to check the sauce. Stain with the finest stainer you have. You shouldn't have to add much salt if any at all.
Hope that helped.
