I'm very tired now and need to go to bed, but let's.
The Iraq vote was not an explicit approval of invasion by the US Senate. It's an authorization to use military force subjected to the command of the President. She's explained that she had a good working relationship with W in the aftermath of 9/11; in her speech on the floor, she stressed that she trust the President to do the right thing, and he didn't. Now, you can question her judgment on the matter, but on that ground let's denigrate John Kerry, Joe Biden et al. as well. Fact of the matter is W and Dick Vader misled the US and the world about WMDs in Iraq, and the blame lays principally on the two of them, along with the neocons that made up W's foreign policy team. Does that exonerate her from any blame? No, but in the broader context, it's not her fault chiefly that those children in Iraq died. Since then, she's gone on record numerous times apologizing for it and explained the reasoning behind her vote. I don't care if you believe her, fact of the matter is that she apologized.
Now move on to Sanders and the gun victims families. The arm manufacturing industry is the only one protected under US laws from litigation against their products. Saying that they sell their products legally is missing the big picture. The fact is that they've aggressively spent money on lobbying to repeal assault weapon ban and flood the market with military grade weapons that are highly destructive in the wrong hands. If the auto industries release fecking tanks that feck up the environment, road and endanger people, those affected can go after them. Why not the gun industry? What do they have to fear? Sanders is running for the Democratic nomination, and gun control is one of the policy pillars of the party. The families of victims want to know he'll be an advocate for them, they want representation. They ask for an apology to that vote, just as much of the base asked Clinton for her Iraq vote. He didn't apologize, because he feels he's in the right. That's his right, just as well as the right of the families to ask for that apology. Now you can speculate about the Clinton's campaign involvement in this request, but I hope you won't dismiss the legitimacy of their grievance.
As for your last points, lobbyists and bundles often represents multiple industries. I can't see how in translates to Clinton's support of the gun industry. She holds an F rating from the NRA. Her vote reflects her position, no matter the gun lovin' show put up in '08.