Gun deaths have declined for 25 years, so your first question is irrelevant.  

We accept deaths by dozens of causes every day without calling for mass restrictions on their use.

"the Sandy hook shooting was done by a man who used his mother's guns."--No, the Sandy Hook shooting was done by a socially-maladjusted nerd who used guns that weren't actually his, and killed his mother in the process.  That's hardly a great example for why every gun transfer should require a background check, unless you have proof that most murders are done with private-sale guns.

And I'm more than willing to treat firearms EXACTLY like we treat cars.  IOW, I'm willing to go through licensing, registration, and insurance for owning a gun if you're willing to make the license SHALL ISSUE, I can buy any gun I want across state lines without having to go through a dealer, and the license renewal consists of a simple vision test.  And not all states require a driver's safety course, you know.