general attacking questions

[fastphil]

The first thing you should have discovered is the Disruption rules the game. As you have said you can not assault if you are disrupted. Also you will find it near impossible to hold ground agaist a near equal foe and your direct/indirect fire will be less effective.
The Soviet army is built around assault- once you have softened up your opponent a If you want to eliminate enemy units disrupt them, surround them, and then assault them. Since they have no retreat they will take additional loses. The better way, if possible is disupt them, give them a retreat path you control while isolating them and then assault them. Most times they will retreat giving you the hex, they will be disrupted, isolated and unable to become undisrupted (because of isolated). Then you close in, leave them no retreats and assault them in the more favorable terrain. If not favorable terrain keep moving them back until they are in more favorable terrain and then go in for the kill.

In Sicily use your naval, air and artillery to disrupt the coastal units. Any assault capable unit should them be able to retreat them.
But remember the Allies landed in a storm unprotected beaches and this was their first landings where they would face the Axis on the beaches and not Vichy. The Big Red 1 did not start out being the killer elite but was honed in combat so you might have higher expectations then you should at this point in the war.