Yes, it’s a legal saddle and can certainly be used for local H/J shows.
Black tack is uncommon in hunters, but not unheard of.
However, I recommend against it. I consider “All-purpose” saddles to be “No-purpose” saddles. They are not forward enough for jumping, I personally wouldn’t do more than crossrails in them, and you said you’d be showing at 2’6’’. They also don’t really put you in the right position for dressage. You’re betting off getting a Close Contact saddle, which will be safer for jumping, and you can still lengthen your stirrups as needed for dressage (about up to First level) and trails.
I have no opinion on it being Wintec, as I have never ridden in one. I personally do not like synthetic saddles and only purchase/use/ride in leather saddles.
I have a Collegiate jump saddle (wool flocking) and just bought a Bates dressage saddle (CAIR panels) with the Easy Change Gullet system - I absolutely love this feature. There is a measuring device you can purchase that will tell you the tree plate size to use. Videos on Youtube show how to use it properly.