Hmmmm...simple math just doesn't add up.
4000 x 4 days a week = 16000 yards
16000 / 1760 yards (mile) = 9.09 miles per week
And you're planning to attempt a 30+ mile swim at one time in 6 months from now?? Honestly, you either need to change this goal swim, or you have to have a serious increase in pool/OW practice time.
I've never done a long distance swim like that, but I can tell you that 4000 yard practices a few days a week won't cut it for a 30 miler swim.
4000 yard practices will barely get you ready for long distance pool swims.
Need to up your swimming distances, and get time training in the outdoor OWs as well.