As for TDM - it even drops performance on midend PC sometimes. How optimized it needed to be to run on tablets i can't imagine... Unity otherwise has free version, editor and can build straight to tablet or iphone I think bulding level in unity will take less time as theres no need to snap to grid, can seamlessly insert geometry from blender, has script editor, motion system for human ragdolls and so on... The other thing that paid version offers more optimization and visual options. And mobiles kinda bad at dynamic lights.