Employment history
I would work backwards. Current or last employer at the top, then previous employer, and so on. Put down your job title, primary duties performed, and name and title of supervisor. If you left on a negative note, I'd list someone in the company who will speak positively about you. List accomplishments, such as promotions, achieving Gold Seal CFI status, employee of the month, etc.
I would not provide a reason for leaving the job unless it is requested because it might read poorly on paper, even if it was for a good reason. Let them ask you why you left a job(s) during the interview.
You also want to account for all of your time between jobs and try to list a contact who can vouch for those gaps.
This is also a time to gather LORs from each job, if you haven't done so already. Good, positive LORs just might obviate a prospective employer's need to call a former employer. The wrong person might answer the phone and not remember you, deny you ever worked there, or just plain badmouth you. Most employers these days will verify only dates of employment, position and salary, but ya never know what someone might say about you.
Hope that helps some more. Good luck with your job search.