if the enemy hidden baldes my guy and then i sacafice do I draw 4

No — you draw 2, not 4. Sacrifice's kill is an additional cost paid before it resolves, so by the time your opponent's Hidden Blade resolves, your unit is already in the trash. Hidden Blade's "Its controller draws 2" is a linked instruction to its "Kill a unit" instruction (Rule 359.3.e.14) — when the kill can't happen because the target is gone, the draw is ignored too. You still get Sacrifice's draw 2 and channel 1 rune exhausted; the enemy gets nothing from their Hidden Blade.