You can change this by editing nw_s0_evardsa and nw_s0_evardsc.
As it is now:
nw_s0_evardsa
122 | eDam = EffectDamage(nDieDam, DAMAGE_TYPE_BLUDGEONING, DAMAGE_POWER_PLUS_TWO);
nw_s0_evardsc
122 | eDam = EffectDamage(nDieDam, DAMAGE_TYPE_BLUDGEONING, DAMAGE_POWER_PLUS_TWO);
For +1 instead:
nw_s0_evardsa
122 | eDam = EffectDamage(nDieDam, DAMAGE_TYPE_BLUDGEONING, DAMAGE_POWER_PLUS_ONE);
nw_s0_evardsc
122 | eDam = EffectDamage(nDieDam, DAMAGE_TYPE_BLUDGEONING, DAMAGE_POWER_PLUS_ONE);
The grapple logic preceeds the paralysis check. Grapple determines how many of the tentacles aimed at the target succeed. Since it compares
nTentacleGrappleCheck = d20() + nCasterLevel + 8; vs nOpposedGrappleCheck = d20() + nOppossedGrappleCheckModifiers;
where
nOppossedGrappleCheckModifiers = GetBaseAttackBonus(oTarget) + GetAbilityModifier(ABILITY_STRENGTH, oTarget); (and +4, or +8 if large or huge)
i.e. if a level 10 wizard casts evards vs a level 10 human fighter, up to seven tentacles will try to grapple the target with an opposed check of d20 + 18 vs d20 + 14 or so highly likely 4-6 tentacles will hit the target per round. If a target is hit in a round, it rolls fort against paralysis (duration of paralysis is one round)