Well, I was actually able to book the itinerary over the phone (The first guy said I can't cross two oceans and that it has to be an around the world ticket, but then he transferred me to star alliance and they had no problem booking my ticket).
IAD-NRT//ICN-LHR(stopover)-IAH
Now my question is, what counts as an open jaw? I was wondering if I can add a leg from somewhere else in Texas to IAD, like Dallas or San Antonio. Would that be possible? I'd like to add that as soon as I can, if possible, to avoid any additional fees.