No the airdrop will be a percentage of the total (future) available coins. The dividends are generated from the 5% transaction fee on the marketplace. Theoretically if you hold your safex coin for a very long time the amount of safex cash will exceed you coin holdings (but I am talking many years). Other ways to obtain safex cash is via mining and/or selling something on the marketplace. Very likely they will also be listed on online exchanges.
Yes, somewhere Q2-18 this will all happen - the whitepaper will be released soon and in there the process for registering your wallet address to receive dividends will be described into detail.