On the first point, assuming no significant changes since I last looked at the code (and the fact tpruvot does not hold great interest on the trading side):

1. Coins are periodically sent from the wallet to exchange, leaving a percentage reserve balance.
2. When the coins on the exchange account reach the minimum trade size on the exchange, they are dumped on the order book, ripping up to something like 5 layers bids if necessary. Any remaining partially filled orders are automatically cancelled if they exceed the mid price.
3. When a BTC account threshold is reached (configurable), the BTC is automatically withdrawn to the yaamp wallet. BTC exchange fees can be quite high on some exchanges (last time I looked 4mBTC on Cryptopia!)
4. Rinse and repeat. There is no strict tracking of what happens to individual user balances on the exchange process.

So leading to the second point, I'm not too sure how yaamp/yiimp determines a fair distribution of users earnings. The pending should be treated as an estimate for sure as it is not a done deal. But once the deal is done, there is no way of saying your chunk of a particular coin was executed on a specified exchange, at a specified price on a specified order.