Did you air-down your tires any? With that much snow and an open axle, that'd be the thing to do while it's warming up.
My Jimmy (running 3-days straight now! Fingers crossed) has the standard 1/2-ton open 10-bolts. The (31x10.5R15) BFG KM mudders do pretty good in deep snow (less so on ice), but being a diesel, it really wants to spin at tip-in because it makes all (YMMV) its torque pretty much off-idle. When I drop down to 20 pounds or so (city driving), it really grips a lot better with signicantly less spinning.