1) The standard proportional payout is Contributed shares % times 50 BTC (or block shares given / block shares total x 50 btc)
so, if you contribute 1% of a certain block round's shares, you get rewarded .5BTC, .5% = .25BTC, etc.
Your first flaw is in assuming there's something inherently fair about the Proportional method. This usually comes from the misconception that people can make progress mining. The fact is that over 99.99% of shares are
completely worthless and do absolutely nothing for the pool. They have
no relevance whatsoever to the block that might (or might not) be found at the end of the round. Only 1 share finds that block, by itself, with no help from the other shares.
The goal of pools is to pay miners for lower-difficulty fake "blocks", while collecting the rewards itself from the
real blocks. This reduces variation for the miners. Proportional is simple, but by far not the only way pools might decide to pay miners. The most fair method, with least variation, is to pay them 1/difficulty for each difficulty 1 share: this is called Pay Per Share. In comparison, Proportional pays miners
more than their fair (PPS) reward when it finds a block quickly, and
less when it takes a long time to find a block. Because of this uneven distribution, it is most effective to implement "pool hopping" to mine on the pool currently offering the highest reward per share (ie, the one with the fewest shares in the current round).
Straight PPS was originally implemented by OneFixt2 for BitPenny, and is a popular option at Deepbit despite their 10% fees. However, it is more vulnerable to true cheating, and when this happens, the pool operator takes the infinite hit from it.
Eligius has (after much notice and even poll from members) switched to a system almost like PPS. Miners are generally paid the full 1/difficulty reward for each share (without the huge 10% fees historically associated with PPS), but the system keeps track of what the pool has itself earned overall, and limits payouts to ensure the operator does not take a hit when there is cheating or extreme unluckiness going on. At the same time, it tracks what miners would have earned under straight PPS, and if someone was ever underpaid (due to not having the funds available) will pay them a bonus later if it has extra funds (from lucky/short blocks).
All the payout systems will eventually tend toward the same total payout over time, with one exception: due to the proportional method's predictable unfairness pattern, miners can achieve 30% greater earnings than their work's fair pay. Those who do not implement pool hopping, see an effective 30% loss over time. This is the primary motivation for avoiding the proportional system.