How exact is this? Pilot attribute and weapon attack (FP, refits, R&D, features, suitability) match the game exactly; the hit chance matches 98% of the game's hit rolls.
Crit chance = crit rate × (1 + features) + crit rate added after features + the crit-points term (your crit points vs the target's crit resist) − the target's crit-rate resist; this matches the in-game attack preview.
Buffs gained during a fight (stacks, triggers) are not modelled unless you switch them on or set their stacks under Situation; use Extra bonuses for anything else on your unit and the target's Other buffs on it for anything else on the target.
DMG_per_shot = (srcAtk × AtrDef_coeff ÷ Nshots_base − eArmor ÷ 10) × SkillM × (1 + DMG%) × (1 + eDMGFactor%, when the target has one) × (1 + FinalDMG%), × (1 + CritDMG%) on a crit. Accessories trigger once per attack; hit and crit roll per shot.