Texas Tuition Promise Fund Questions?

We purchased a Texas Tuition Promise fund which is currently worth more than what it will pay out. This is our first time to use the plan we bought back in 2009. We need to use this for Out of State Tuition. I am considering taking a partial cancellation payment for 50 units (we have 400) which is equal to more than what they would pay if I had them send the benefit directly to the University. What am I missing here??. Should I transfer the entire fund to a 529 plan?

If I take out the 50 units and have the payment sent directly to the university, am I missing out on future gains in the investment?

Has anyone used all their units and had money left over due to a positive investment return?

I have a flight student, so we will have to pay from savings as well to pay for his expensive flight fees.

Thank you.