This must be having an awful affect on the kids, my advice would be for you to leave at least for the time being until he sorts himself out. Its not an easy option but at the kids ages with school to deal with as well its just not fair for them to be living in such a volatile environment.
find somewhere to go, or phone up the womens refuge, either way get away for a while to give you and your kids a break from walking on eggshells.
from experience I can tell you that kids want a happy stable environment, I bet they have become withdrawn as a result.
do it for them, if only temporarily at the very least