Think once youve got your shocks sorted you will notice a big improvement.
A few things you could do to cure your problem of the rear end breaking away when pushing the car are:
1. Take off the rear anti-roll bar to give you more rear end grip.
2. Stand the rear shocks more upright by putting them in hole number 2 or 1 on the shock tower. (this will help the car straighten up under power coming out of corners)
3. Put the front shocks in hole number 2 on the front shock tower (this will give you more initial steering but less on power steering, again stopping the front end from rolling midway through a corner and pulling the back end round).
4. also make sure you have three degree toe in on the rear, any less than this can make the car feel loose especially at the rear.
Set ups are about personal preference but these tips should help sort out your problem.
Craig