i think it might be wise to take his MOTHER out of the equation. none of this is really HER fault....it's stuff between you and your husband. and your husband happens to have a serious drug problem and is currently allowed to waltz in and out of the house at a whim.
i know you are biding your time but meanwhile he's destroying what is left of his business (i presume) and probably wiping out the finances as we speak. i don't think you really HAVE the luxury of time here...not with the ticking time bomb known as meth addiction in your life. i'm not sure i can express just how bad this is....