I adore
Eve much more so than
Eva. In fact, I'd use it if my surname also didn't have one syllable. As it is,
Eve is one of my favorites for the middle name spot. I think it suits your other names quite nicely.
Re: combos,
Eve would complement a variety of names. I won't make a list here except to say my favorite combo is
Eve Juliet which I think is just regal and stunning in its simplicity.