if your not experienced on icy roads the best thing for you to do is what you did after going into the ditch and slow down. 4wd will help you take off faster but wont save your bacon when stopping.
oh and its never a good idea to go 90 on ice lol. good to hear you made it out fine.
when driving the slush in the middle of the road i usually will keep my foot on the gas but not accelerating, and slowly creep over holding the steering wheel tight. never pull on the steering wheel when driving through slush.