Here is a good resource for this info: http://wiki.bitshares.org/index.php/Bitshares_X
But to give you some basic answers:
1) Initial alloc. was 50% / 50% based on PTS and AGS holders. PTS (BitShares Protoshares) is a minable PoW coin and AGS is basically a donor list from the AngelShares crowdfunding campaign. One is liquid and the other is illiquid.
2) BTSX aren't pegged to BTC. But there should be bitBTC available on the BitSharesX market as soon as enough delegates publish feeds, which would be collateralized by BTSX.
3) In response to buying assets on margin, I think this is the inverse of what shorting bitUSD does? As that is selling assets on a margin... but don't quote me on that, I am learning about markets and economics everyday. So my unofficial answer to your question is no.
4) Non pegged assets sound like what other decentralized exchanges may offer today, such as the NXT marketplace. They are user issued and thus you have to trust the user to back the value. Market pegged polymorphic digital assets like bitUSD / bitBTC / bitCNY are different because the value is determined by a consensus of the participants in each market rather than a user.
5) You can trade USD -> BITUSD here: https://bter.com/trade/bitusd_usd
6) Users can create assets on the market but the cost is expensive. Another DAC is planned to handle user created assets for much less cost, called BitShares ME.
So FREE, LOVE, LAB are all user created market assets. They won't be tradeable until at least 50 delegates publish feeds for them and the required market depth is reached, I believe.