if you want to do split balance in the air. Try to do balance on the yoga block first.
Split Balance is not only about flexibility but strength.
after you can do front split on the floor,
-try to engage your Hamstring + Hip Flexor + Hip Adductor in the same time to lift your hip up from the ground
-put yoga block under your calf (easier than your heel) and try to hold your hip in the air.
PS. Fabrice wrap around your calf is much easier than wrap on your ankle (if you do footlock