I want to punch this idiot in the face, how old is he??
The CM is lying - is she a personal friend? Because when there is something wrong with your car you phone a friend, not your mindees father. For that reason alone, id sack her, it implies that she initiated the "conversation". IF it were true, your dh would have said, oh yes, i forgot to tell you the CMs car was playing up and i helped her out, she would have mentioned it to you too - "oh, your DH was great helping me with the car etc" - come ON LOW wake up and smell the coffee, i know its hard but you deserve so much better than this.
You need to get a new CM for starters - she is taking the piss, do you really want this woman looking after your children and weedling her way into their lives?
You say he probably wont come home tonight - well good. Do you own your house? Is it rented? Whose name is on the rentbook, mortgage? He don't come home tonight, first thing, you go and change the locks.
Your children deserve a father who loves and respects their mother. I can't say whether he loves you, but he certainly don't respect you .
I know you don't want to believe it, i can totally understand, but i think deep down you know that he has done the dirty. From what ive read into this thread its not the first time he has treated you badly. So what if its good sometimes, You want someone that it is good with ALL the time, not fairy tale good, we all have ups and downs, but they don't include infidelity, lies and lack of respect.