Few questions

1 I wonder how cactus and cape of specter and knus work together And each item effect too Example, if armor is 100 and if the 100 armor reduces damage 50% then, Does 40% armor ignore mean 100 armor becomes 60 or 50% reduce become 20% ? 2 how specters sets work(focus lost and reset multi crit) with multishot(holgar, crow, rabbit ects) when one of targets lose focus all multi cri resets?