TX is competitive and rarely do they ever duplicate. In other words those on your Cong.slate will most likely be on the Senators. I think maybe every year there is a poster that might get two noms from TX, but it is rare.
Of course you apply for the VP.
I think you should go to the nomination forum here and look at the stickies. You are confusing charging with being on a slate. The VP can only be charged at any given time 5 cadets. However, once you have the nomination, USAFA can bring you in from the national pool.
If you do the math between MOC, Presidential and VP charges, they are only half of the incoming class appointments.
Apply for the VP, but also be honest with yourself. If you have not applied for an AFROTC scholarship get on the ball now because their first board will be meeting in a few weeks. I don't know their cut off date for the Dec. board, but you might still have time.
Good luck.