1. Very easy. They were big tournaments in the pre open era which were not majors. They are Masters equivalents. The other tournaments are 500 and 250 equivalents respectively.
2. Don't understand the question.
3. Simple - a basis is the current point system. Then the pro majors are similar to the current ATP finals - the best players played there. The amateur majors were big events but with a smaller competition than the current. Half of the points is fair.
4. Here I have to write a lot. But example with the pro majors - W 1,500; F 900; SF 540; QF 270; R16 135. The same principle as the current point proportion.
5. It is logically consistent and fair because it uses the same principles of the current tour and tournaments specification.
But all this requires a huge work.