Don't give up now!! You're just having a down day. Everyone has that and you have been doing so well. Don't read too much into what Dave36 says. He was just venting. This is our ranting place so don't be too disheartened by what you read. I am sure he loves his wife dearly or he would not be here trying so hard.
Step back and ease off some of that pressure of yourself. What matters most is that you are trying. As you know, most HD spouses we have around here are in total denial and therefore not even trying. We'd all give anything to have our Hs/Ws just TRY!
You said "I'm trying so hard to be a good wife but I just can't do it." Don't be so hard on yourself. Although this is an SSM forum and discussions are focussed on this area, I am sure you know deep down that being a good wife is so much more than just working on this area of your life. And we all know that you are working hard in trying to understand your Hs POV, in trying to communicate with him, in understanding his LL and trying to fulfill those. Intimacy is an an important area to work on but then so are being a good companion, confidant, good mother, I could go on and on. So don't be dishearted and keep up your good work.