Category 1 (contracted, with UEB modifiers) is the best for this Spanish, since there’s only a small amount in an overall English context.
I don’t think there’s a good basis in any guidelines for moving the Spanish text, and it’s unclear if moving it would make it more helpful. My advice would be to add a note on the TN page (or on the first page, if there’s no TN page) saying something like “Spanish information available”. I don’t know if you can say much more than that, because the brochure doesn’t even say where the Spanish information is! But I think a TN will be the simplest solution to this problem.