Okay...first, your husband is almost certainly in Replay. Depression permeates ALL stages of MLC and MLCers cycle emotionally...so since the divorce process is new, he may seem to be depressed or withdrawing.
Read the resource threads at the top ot thie forum.
Read Men in Midlife Crisi by Jim Conway. Look up midlife books at your library...just keyword 'midlife' and at Amazon.
If you can, stop the divorce...and at least stop doing anything to push it along. This is going to be a long ride...so prepare yourself by reading.