"I swear!" (6)
(Another definition for so help me that I've seen is " On my word".)
(Other definitions for honest that I've seen before include "Objective mediator" , "Honourable, sincere" , "Honourable, true" , "Straight up" , "Without dissimulation or guile" .)
(Other definitions for honestly that I've seen before include "Really; truthfully" , "Frankly -- that's outrageous!" , "In truth" , "Truly, without a word of a lie" , "In a fair-dealing way" .)
(Other definitions for no joke that I've seen before include "Not a trifling matter" , "A serious matter" .)