No damage to Scorch. For half numbers always round down. So you only take 4 damage.
Preserver > Breecha > Mack > Kessel > Scorch > Claw
Ray of Frost - (1d20+5, 1d8)
1d20+5 : (2) + 5 = 7
1d8 : (1) = 1
Poison Spray - (1d12)
(8) = 8
CON vs Poison (disadvantage) - (1d20+2, 1d20+2)
1d20+2 : (2) + 2 = 4
1d20+2 : (13) + 2 = 15
Added Hex Damage - (1d6)
(2) = 2
Scorch vs Breecha - (1d20+4, 2d6+2)
1d20+4 : (18) + 4 = 22
2d6+2 : (46) + 2 = 12
Claw Fire Damage - (1d4)
(3) = 3
Claw putting out fire (DC 10) - (1d20+2)
(9) + 2 = 11
Thunder wave damage - (2d8)
(51) = 6
Death Save - (1d20)
(5) = 5
Scorch Con Save (Disadvantage) (DC 13) - (1d20+2, 1d20+2)
1d20+2 : (12) + 2 = 14
1d20+2 : (17) + 2 = 19
Claw Con Save (DC 13) - (1d20+1)
(7) + 1 = 8
Poison Spray vs. Scorch - (1d12)
(4) = 4
Hex damage - (1d6)
(4) = 4
Scorch Con Save vs Poison (disadvantage) - (1d20+2, 1d20+2)
1d20+2 : (7) + 2 = 9
1d20+2 : (6) + 2 = 8
Attack on Mack - (1d20+4, 1d10+2)
1d20+4 : (5) + 4 = 9
1d10+2 : (3) + 2 = 5
Death Save - (1d20)
(4) = 4
Medicine - (1d20+2)
(6) + 2 = 8
Repair (Medicine) - (1d20+3)
(10) + 3 = 13