It's not a Federal Sales Tax. It's the same state sales tax that you pay when you buy something locally. Actually, the current tax code says that you're already supposed to be paying this sales tax on items you buy online, but the problem is that these companies currently can't charge your state's sales tax at the time of purchase unless they have a physical presence in the state. So, it's up to you to pay this tax separately when you file your taxes every year (like anybody actually does that). The states actually lose quite a bit of revenue because of this. The only thing this bill would change is it would allow the online companies to charge your sales tax wherever you are.
And the sadder part is, we still don't know what actually DOES cause autism. Perhaps if the researchers were allowed to spend more time on that rather than proving over and over again that the cause isn't vaccines, we would be a lot further along.
Supposedly infinitely small (or on the scale of the Plank length, depending on who you ask), but that question is of no concern here. The physical size of a black hole is defined the size of its event horizon, which depends on its mass.