You haven't listed a single relevant defensive threat.
252+ Atk Thick Club Marowak-Alola Flare Blitz vs. 248 HP / 96+ Def Thick Fat Venusaur-Mega: 218-260 (60 - 71.6%) -- guaranteed 2HKO
252+ Atk Thick Club Marowak-Alola Fire Punch vs. 248 HP / 96+ Def Thick Fat Venusaur-Mega: 138-164 (38 - 45.1%) -- guaranteed 3HKO
252+ Atk Thick Club Marowak-Alola Shadow Bone vs. 248 HP / 96+ Def Venusaur-Mega: 154-183 (42.4 - 50.4%) -- 1.2% chance to 2HKO
252+ Atk Thick Club Marowak-Alola Flare Blitz vs. 252 HP / 144+ Def Hippowdon: 217-256 (51.6 - 60.9%) -- 94.1% chance to 2HKO after Leftovers recovery
252+ Atk Thick Club Marowak-Alola Shadow Bone vs. 252 HP / 144+ Def Hippowdon: 153-181 (36.4 - 43%) -- 98.2% chance to 3HKO after Leftovers recovery
-1 252+ Atk Thick Club Marowak-Alola Flare Blitz vs. 248 HP / 244+ Def Landorus-Therian: 160-190 (41.9 - 49.8%) -- 90.6% chance to 2HKO after Stealth Rock
-1 252+ Atk Thick Club Marowak-Alola Shadow Bone vs. 248 HP / 244+ Def Landorus-Therian: 114-135 (29.9 - 35.4%) -- guaranteed 3HKO after Stealth Rock
Without Flare Blitz, you get stopped by Mega Venusaur, Hippowdon, and Landorus-T. You know, actual defensive threats.
Hell, you even struggle against Chansey.
252+ Atk Thick Club Marowak-Alola Fire Punch vs. 4 HP / 252+ Def Eviolite Chansey: 258-304 (40.1 - 47.3%) -- 47.7% chance to 2HKO after Stealth Rock
Ok but if you're using Alowak to try to stop fat grounds, or even mega-venu, you're using it wrong. Alowak doesn't stop defensive threats, it stops offensive threats, such as Tapu Koko, Genesect, Pheromosa, Magnezone, and any fighting/electric type without SE coverage, and so these calcs aren't really relevant to the meta. If any of these switches in, they're going to take a big chunk from Shadow Bone, and then you're going to switch out. Your calcs show that Alowak can't even OHKO any of thse with max attack blitz, so what's the point?
Save health, stick around longer, block more volt switches.