There is officially no maximum on how many times a year you can use the Visa Exempt Entry by air, but every time you have to hand over your passport to an Immigration Officer who has a duty to check why people come to Thailand.
There is a small difference, it will be the same period of 30 days Visa Exempt Entry and you can also extend this once with another 30 days but you can only enter twice a calendar year by land borders using this 30 day Visa Exempt Entry Scheme
Correct, it will be case by case as different people have different incomes and it will be impossible to write out all the options.
But Document in foreign languages must be translated into Thai. If translated into English, it should be notarized by notary organs or the applicant’s diplomatic/ consular mission.
No, you do not continue to be inside Thailand when you leave.
You start counting again as day of arrival as day number 1 and count towards 75 days to get into the period of reporting that you are almost 90 days consecutive inside Thailand.