Finally I have managed to mod the eridium.
Axton level 20.
It's my recent save at about halfway playthrough 1.
It has 999 eridium and I also have set the money back to max.
In the menu it only shows 99 because it cannot display 2+ chars.
I'm currently looking for the address of the max backpack capacity.
If anyone needs his own save modded then let me know.
I'm also thinking to mod the eridium in all saves from the level 6 starter pack.