I think you and your husband could benefit greatly from a Retrouvaille weekend. See the website, http://www.helpourmarriage.org for dates and locations. Also, be sure to read the section on the 4 stages of a marriage. You have probably reached (as we all have here) the Misery Stage. Retrouvaille can help. The weekend saved my marriage when we were at a severe crisis point. It is NOT counseling. It is a weekend together with your spouse thinking about your past and your future. It is very positive, and does not rehash a lot of garbage. In fact, it puts the garbage out for good. After the first morning, there is no more bringing up the past! (Even whe you get home.)
You will learn to communicate in a positive way with your spouse. You and he will both learn to listen to each other with a new kind of openness.
From your description of the situation, I think your husband is trying to do what you want. His letter is very honest. You need to listen openly without preconceived solutions to his problem. And he needs to listen to you also without preconceived solutions. Retrouvaille will give you the tools to solve your problems without medication, psychologists or counselors. It is completely a self-help group -- couples who have succeeded in healing their marriages showing other couples how to do it.