I would ask/argue that loosing wildshape does not automatically cancel the grapple. But that is me hoping for the best.
Did the attacks wrong and applied disadvantage instead of advantage. Hit Bite = 15, Claw = 20
Additionally, while you are transformed by Wild Shape, you can use a bonus action to expend one spell slot to regain 1d8 hit points per level of the spell slot expended.
Rolls
Dex - Save DC 14 - (1d20+5)
(18) + 5 = 23
Reckless Bite vs invisible - (hit:2d20l1+9, dmg:1d8+5)
hit:2d20l1+9 : (63) + 9 = 12
dmg:1d8+5 : (7) + 5 = 12
Reckless paw vs invisible - (hit:2d20l1+9, dmg:2d6+5)
hit:2d20l1+9 : (111) + 9 = 10
dmg:2d6+5 : (44) + 5 = 13
Moon Druid Combat Wildshape healing - (3d8)
(683) = 17