Welcome to the Blitz, Bull. I think you'll find a wealth of knowledge here in terms of SB...
The AI is adequate when playing on defense. Offensively it tends to bog down and do silly stuff, so I'd only play the AI when you are the offense. It's good enough to give you a feel for the mechanics and engine. This may take a little time, but once you become familiar with the system, it really gets fun.
H is Heavy Weapons. D is Demoralized. Disrupted does not show up on the top of the counter, but can be seen when clicking on the unit.
As for documents and tables in terms of resolving combat, there are no formal ones that you'll see on the screen, you'll have to assess this yourself. Like in real combat, you'll want to have a significant man advantage over any hex you're trying to assault. 2 to 1 minimum, but higher is better. Morale of your troops plays a big role in determining the outcome as well. Assault with a bunch of C and D morale guys and you'll probably get repelled unless you've got a whopping man advantage. The terrain the defender is in plays a role as well. If they are in a fortified hex, uphill or downhill from you, their morale, their state (P, D or disrupted) all play a role in determining an outcome. There is no simple equation that will tell you if you'll be successful or not, just like in real life. Assault only when necessary and only when you've got a significant advantage. Failing an assault pins your troops. Over assaulting is something that new folks tend to do. Firing at an enemy from your weapon's maximum distance is also something new folks tend to do as well.
Read the section on Hold Fire, which is important. Hold fire is your friend, especially early in an engagement. You won't waste AI pot shots at units moving near you.
Check out the Important Threads at the top of the page about rules and the like. It's a good primer. Also, check out the site in my signature. There are a bunch of
tactical articles in there that go into great detail about the mechanics of the game. It's a good place to start...
The manual has a lot more useful information than it seems, but being unfamiliar with the system, it might not seem so right now.