1. I think it's the "overconfident & proud syndrome." They're convinced that they're powerful and pay for it with thrir lives. Part of the reason is because Sith idealogy teaches that passions give them strength, and well, a number of teens & young adults are just full of it. They don't need a psychiatrist, they just need to get over themselves. Too late....
2. Well the situation was lopsided in that hanger, with BOMBS dropping from orbit. He (pointlessly) brought friends with him when he hunted Revan. Of course, Calo's got an ego the size of a cruiser, and clearly would've preferred death than accept the fact that Revan was better than him. For Malak & Admiral Karath though, Calo wasn't exactly a prized asset so he was expendable to them.
3. Well, in the time period of the movies capital ships had heavy shields. Hard to say what was going on with the Sith ships in this time period.
4. Yes, but the Death Star was designed for the sole purpose of blowing things up. The Star Forge however could generate an endless fleet.....something 100x more complicated than a superlaser.
5. Well, Malak wasn't very bright.........
6. See #5
7. That's because Revan always was the MASTER. Malak was just a groupie who had muscle but not the brains.
8. I don't think the Leviathan's crew was exactly 100% functional immediately afterwards, with the Admiral DEAD and all. They could barely fire one turbolaser at the Ebon Hawk, let alone operate a gravity well projector.
9. Malak didn't think Revan could handle the droids. Afterall, they were the SPECIAL Star Forge droids. For furthur reference, see #5 above.