You will need the reference letters of the jobs you are claiming the CRS points, for receiving the ITA.
1) The work reference letter must include your duties and responsibilities as per your NOC, CTC, hours worked per week, designation and joining date. This must be signed by your immediate manager/HR
2) Check out this link -
http://www.canadavisa.com/canada-immigration-discussion-board/threads/nail-the-challenge-of-getting-reference-letter-from-current-employer.397796/
3) If you are claiming points then Yes. Otherwise you can move it to the personal history section.
If you already have 3 years of work experience then your CRS points max out, (assuming you only have foreign non-Canadian work experience.)