Yes, it would. That doesn't alter the fact that it is the correct public policy position.
About the same as tabacco or alchohol, I'd think. You just couldn't sell it to minors.
I doubt it. Possibly marginally easier for legal adults, but I can say with certainty that it would be harder for underage teens to get them, as it's currently easier for an average high school student to obtain marijuana or ecstacy than alcohol or tobacco.
Probably not. In many areas of the country it is easier to get pot than beer for those underage.
For older folx, it might make it somewhat more available, but beyond the initial spike as it was legalized, use would probably remain about what it is now. Overall, given the massive evil that comes from the WOD, legalization is the only sane solution. This is of course why it won't happen.
Yes. But the assumption in your question is that more people will use them if they are easier to get them. And the (dare I say a priori?) assumption beneath that is people are such undiciplined and corruptable pools of lusting protoplasm, that, at the mere hint of a sanctionless way of destroying themselves and society, they'll gobble it up out of a mindless reflex.
To this I say bullshit. 