Hey girl, I am a SAHM too! I go to college online so that I can take care of my 5 year old and my 9 month old. This year I *almost* dropped my school down to part time so that I could get a full time job. I decided against it because I felt like I was the best person to take care of the kids.
Yes, it does drive me crazy sometimes! I think it's great that your hubby is good with the kids. You can use that to help you out as well. Since he loves spending time with them, ask him if he minds watching the kids for you after he comes home from work. This way it's easier for you to shop AND you get some quiet time to yourself. Maybe on his day off he could watch the kids while you get some more "me" time for running or doing whatever.
I also think that you should talk to your husband. Let him know how he's making you feel. You're doing an important job and he should appreciate t.
http://www.stayathomemom.com/wordpress/ is a good site for stay at home moms. You could try online college (I LOVE it!) you could also try scrapbooking. Your oldest can also help with some chores like picking up.
Good luck!