Siberian Elm isn’t terrible firewood, but you’re right that it’s slow to dry. You’re probably better off cutting it into rounds and letting it dry in a stack. The brush is also much easier to manage alive than dead and brittle.
As far as removing it, well, they can be pretty nice big trees, but they seed aggressively and usually hold a lot of dead, so they look pretty ugly. If a lot of your row is Ash right now, it probably won’t be in 5-10 years. That may increase the Siberian’s value.