Confuse about Sphere of Protection

I remember that when skill reach Lv12, the Total damage modifier is at -8%
but at its higher level of 18, the value becomes -4%?

so what is this Total damage modifier mean? I deal damage to enemies or they do it to me?

and what is the difference between Total damage modifier and Armor absorbtion? I am confused!

It’s a trade-off skill. You do less damage for more defense.

When the skill is overcapped you do more damage whilst maintaining your defense.

Total damage modifier applies to you. You ignore 22% of incoming damage, but you deal 4% less damage. This increases to 25 and 0 at rank 22.

X% Damage Absorption - you take X% less damage from all sources.

-X% Total Damage Modifier - you deal X% less damage to all targets.

X% Armor Absorption - 100% - X% = damage that leaks through your armor. Example: 1000 armor with 100% absorbtion taking a 2000 physical dmg hit = you take 1000 dmg
1000 armor with 70% absorbtion taking a 2000 hit = you take 1300 dmg

I have tried multiple times
every time i have killed the final boss of AoM (forget the name, the monster related to the quest [The living factory])
but when i explore the map left or right side of the map [ the heart ] i die!

I have over 15K hp and suffer an instance death! why is this?
what can i do to explore the map? is there anything special behind that road?