K.U.
1. Stop beating yourself up for not being "perfect" - nobody is. You have a lot on your plate. How does hubby help out? Does he try to discipline them as well or try to step in to give you a break? Are you both on the same page as far as discipline, consequences, etc.? Can you take some time out for yourself on a regular basis? Or get someone to watch them so you can have a date night with hubby?
2. Secondly, grandparents nearby don't always add stability, and I doubt having them closer would make that much of a difference. My mother has passed away and my MIL is not really a significant part of our lives, plus she lives across the country.
3. If you think your oldest might have ADD or other kind of disorder, have her evaluated.
4. Maybe there is a "parenting coach" (kind of like a Supernanny) that can come in and evaluate the situation - sometimes another pair of eyes can notice things that you might not be aware of. Along that same vein, there is family counseling that everyone can take part in together.
5. Some books you might find helpful - "Parenting with Love and Logic" and "How to Talk So Your Kids Will Listen and How to Listen So Your Kids Will Talk."
6. Again, don't blame yourself totally, but think about your own behavior and what kind of role model you might be presenting. And some people might tell you that the 1/2 ages are more of challenge.
Good luck to you, I hope you can find some answers...