Rule Number 1 (for Q2): be truthful, give a realistic itinerary.
The enter and exit days counts as full days.
Q4: You may not enter before the first day stated on the visa.
Note: Some visas (often first time visas) are issued for a date range. More often a amount of days (duration). If nothing is given then 90 days within a 180 period.
So if the visa is ...
The issueing of Schengen C-Visas, is on the one side restrictive, but on the otherhand practical.
So it is a combination of how the visa was used in the past and the need in the future.
In your case, you have allready fullfilled step 01 (properly used a single business visa).
For the next application apply for a multiple entry business visa (checkbox ...
Usually multiple-entry, long-validity visa are granted after one one more single-entry, short-validity visa without overstay or incident. There are anecdotes of people getting multiple-entry visa to start with, but I don't think that can be forced, and the Netherlands now say they don't do that.