Have you checked if there's availability in J direct to TXL (or DUS) on airberlin? You would be better doing the TATL flight in a flat bed for 40,000 avios and minimal taxes, and an economy filght (either cash or avios) TXL-LON, than spend 39,000 avios plus hundreds of dollars more in tax/YQ on WTP + CE.

Alternatively, have you considered main cabin extra on the AA flight? This would I think be significantly less than the $250 for WTP, would save you the extra avios and you'd be guaranteed decent IFE on the 77W.