Sorry for being absent for some time.
Round 3
Action: rearranging the hiding spot
Move: O32
Bonus Action: Cunning Action (Hide)
stealth check for hiding: 1D20+4 = [19]+4 = 23. That is probably sufficiently hidden and would let Lionel gain advantage.
Round 4
Bonus Action: insightful Fighting check: 1D20+7 = [7]+7 = 14. To be contested by gnoll3's Charisma (deception) check.
Action: Disadvantage due to distance and advantage on hiding, cancels out.
Crossbow attack, with damage and sneak attack: 1D20+7 = [3]+7 = 10
1D8+4+3D6 = [8]+4+[3, 4, 2] = 21. After all that, it was a miss anyway.
Move: stay put