I don't think it's real hard to think up a very plausible fictional reason for why the DS didn't fire on Yavin proper
I just go with the simple explanation that the DS's superlaser isn't powerful enough to have the desired effect on something the size of a gas giant. Not all planets are created equal, nor do they need to be equally vulnerable to a superlaser.
Also, it's a gas giant - what do you shoot? Oh sure, there's a core - but since Gas Giants are almost-but-not-quite stars, I suspect that the core is mostly unnecessary to keeping the planet intact. Blowing up the core certainly wont be good for the planet, but the planetary mass will probably not disperse with it gone. The half hour required to drive around the planet into firing range is almost certainly faster than hanging around waiting for Yavin to dissipate.
(On a side note, I wonder if it would have been possible to shoot THROUGH Yavin? Miss the core, and compensate for the english the planet's gravity would put on the shot? Naw, the gas is probably dense enough that it would mess up the beam on the way.)
The recharging argument doesn't hold up when the Death Star gets used to take shots at individual capital ships...that's going to be dozens of shots.
That was a different Death Star, though with a first generation reactor core. You might as well complain why your Ipod from 2002 doesn't have a touch screen.
Yeah, I agree that the ewoks beating stormtroopers was preposterously pandering. For one thing, what the hell is the point of the stormtroopers wearing armor, which obviously hampers movement at least a little bit, if it can't stop blaster bolts or apparently anything else? I think the ewoks failed to take down one stormtrooper with an attack of...what, some pebbles they threw, or a very crude bow (I don't recall exactly which weapon they used), but everything else they tried worked. The troopers were incredibly inept in that engagement.
1) Terror and intimidation
2) Shrapnel and glancing blows
3) Environmental conditions (heating, cooling, exposure to vacuum)
Also, the Stormtroopers were holding their own against the Ewoks until they broke up into smaller unites and pursued them into the woods. A tactical blunder? Sure, but that's more about the arrogance of the Empire than the effectiveness of their equipment.
Edited by Desslok