Wishing you the best of luck, and do hope the front end doesn't drop through the ice before you get it out, or worse yet, one side goes through the ice (building a platform under it may help) and the tractor tips on its side. I would have more than one come-along or winch tied to this when trying to remove it.
So far, I think you have been lucky with your efforts to get it out. Keep up the lucky streak.
Not a pretty sight, and ice under snow doesn't get too thick, as you already know.