That's news to me.
1. Maximum melee and ranged balance is 80%. What you're saying is that critical hits always deal maximum damage?
2. Does this also apply to skill balance? Example: Ice Spear deals 200-300 base damage. Are you saying that critical Ice Spear always deals 1950 base damage? This would be useful for Crash Shot which has several different skill multipliers.
No. The damage forumula works like this. (Max-Min*B)+Min+(R*Max*C)
B=Balance, R=your crit % C = your critical hit skill damage multiplier.
In the above example of a 0-100, 0% balance weapon You'd get the following damage: For non crits, half of the time the damage would range somewhere between 0-100, and half the time it would be 0-0 (min 1 damage, also strength and enchants not counted, so unrealistic but not impossible to reproduce)creating an average base damage of 25. 30% of the time, a crit will land. This crit will add 150% of Max (150% of 100= 150 conveniently enough). So a crit will half the time be 150+[0-100], and half the time 150+[0-0]. or 175 damage on average. Since crits only happen 30% of the time, you can multiple the extra damage from crit by 30% (150*0.3= 45). So the average damage of a 0-100, 0% balance, 30% crit weapon would be (25+45) 70.
Spells and other skills with set damage work the same way, using the min-max of the skill, and whatever balance and crit apply to them. In the case of IS, magical balance (from sources listed in wiki including mostly INT) and crit (also from specific sources as per wiki). Crash Shot, as you've pointed out numerous times, uses three damage calculations. We'll have to see if each can crit, but probably.