Yes 2 E & F are across from one another, but it's a 5-10 min walk and if you walk you will exit airside and need to re-enter security. I'd advise the airside bus. Be aware that security at 2E is very extensive and takes a bit longer because it's where most of the US bound flights depart.

On your return (flight 49), you will depart from the remote 2E terminal, I think it houses gates E79-87. Look for a special bus from your MAD flight at 2F that goes direct to the 2E higher number gates if you can.
I just did NW49 yesterday, and it does take a while to get to the remote terminal. However, there are stores, cafe and a nice AF lounge in this "temporary" terminal.