I found even if the base fare was more than $100 if I tried to use travel funds to pay the balance after using my LUV voucher it still used up the travel funds first. So I just booked a fare with a base as close to $100 as possible, used a small leftover travel fund creditt I had that was still less than the balance, then entire LUV voucher was applied. I used a credit card for the remianing balance. Cancelled and then got the credit card amount refunded and used the new Travel Funds to book the flight I wanted with a base fare under $100.
I did notice by booking a Wanna Get Away Plus fare the entire travel fund credit became transferable even though I used a flight fund credit to pay for part of the flight that was non-transferable.