I suspect he is depressed.
He is adamant that he doesn't have the skills or knowledge to do the job. He was at previous place for 15 years and doesn't cope well with change.
I'm scared he will end up having a breakdown if he stays but how the hell will we pay the mortgage on our beautiful home. I don't want our DC to lose their wonderful, safe home 
Please give me advice. Sitting here shaking and in tears. Called FIL who is coming over tonight but he started crying too so not a huge help.