Disconnecting the front bar would be an easy thing to try. Unless the hardware is really rusty!
Less easy would be to shim the rear spindles for less/zero toe-in. But it might not be so great when you don't want the rear end coming around!
With your weight distribution, it might make more sense to try to get more grip from the front tires. Maybe wider front tires at lower pressure? On a smooth surface like ice, maximizing the contact patch might help. More siping (or studs) on the ice.
Maybe modify a pair of tires for ice racing. Lots of sipes. Check out the Team O'Neil Rally School YouTube channel for tire videos.
The LSD probably makes a huge difference coming out of turns. I don't remember if you have one.
Add weight behind the seats?
Have you asked other drivers for advice?
How good are you at driving in reverse?
