I haven't had a chance to review the .SAL yet, but in my experience, Heinz57, WestPointer and Laszlo are always dead-on in their respective analysis, so I have no doubt that they are pointing you in the correct direction.
Regarding your specific question about artillery only bombardment...it works, sort of....if you use artillery only, if it is set in minimize losses, it will consume one combat round. If set on limit losses, it will consume two combat rounds. And, you can guess what's coming here, if set on ignore losses, you'll use up three rounds just doing the bombardment. Lord help you if you fail a proficiency check along the way and lose the rest of your turn doing so (and playing the Soviet side in almost any east front scenario is an adventure in failed proficiency checks, believe me!)
Many outstanding players on this site subscribe to using a broken down AT or AA unit to "probe" the defenses of a hex. In otherwords, you deliberately split an AT or AA unit (needs to be something very mobile) into thirds, and you use one of those pieces to perform a limited attack on minimize losses against a hex you want to take. The catch is, all artillery in range is dug in and on ignore losses, so each unit is firing three times with half of its tubes to support this one attack. Losses are usually heavy for the defender over a couple turns with this sort of treatment. We've found (Heinz57 more specifically, if I'm not mistaken) over the course of this tournament that using one artillery unit to directly bombard the hex on minimize losses goes a long way in disentrenching the defending units when used in combination with an assault.
I personally, given the scale and number of places I want to assault in this scenario on a given turn, have rarely used this method. I wind up studying the map closely before doing anything, but usually I look for places where I can gain a flanking attack (and the bonus that comes with it) as where I want to try and gain ground. Then I'll hit that hex from two or more sides with units on minimize losses, one artillery piece directly bombarding on minimize losses, and all other artillery in range not similarly employed dug in on ignore losses...and watch losses mount on the Axis side. Plenty of evaps, plenty of units in the front that are now shells of their former selves.
Another key bit of advice, and then I'll stop typing for the night, is to watch the playback closely...several times if need be, making notes on a sheet of paper to keep track of where reserves are going towards. The intelligence the game gives you is quite limited, so this can help prevent nasty surprises.
After the playback, look over the situation on the map closely. It won't usually be nearly as bad as the playback will have you believeing, though it won't be pretty at times either. At any rate, study the situation up and down your lines before even moving anything and mentally, if not on paper, plan out where you want to advance, with what units, and objectives for the turn. This will help you keep formations together, and generally help your play not be a random point and click festival...though if you've really broken his lines, formation coherency isn't as important as the pursuit into his rear areas and really pressuring him...but that's another story altogether!
Anyhow, keep posting questions and .SALs, and we'll continue to give advice. Keep punishing the Italians in particular....they are super-fragile in this scenario, and if they evaporate, they don't reappear....so your opponent has to strip his line somewhere to fill that hole.
Okay, I think that'll do for now.....
Good luck, tovarich!
John