Changing Job after approved I-140 less than 180 days

[Adilaksh]

Hi,

My I-140 is approved last month and I'm planning to change my employer in a few weeks as my H-1B transfer(premium) to my new employer is in-progress. I have discussed this with my current employer and requested him not to withdraw I-140 for 180 days. But he mentioned that he has to withdraw my I-140 and visa as soon as I leave the company. He also suggested that I could give leave of absence for 5 months and give resignation later. Also he mentioned that he will not be running my payroll during this time but he will keep my I140 and visa active for 5 more months. 

I appreciate if you could answer the following questions:

1. Is this possible? Can I legally stay in US on leave of absence with current employer, at the same time, work for new employer?
2. Will this lead to any complication during my I-485?
3. Can I legally keep my employment active with 2 employers for 5 months at the same time? 
4. How will my W2 look like? He mentioned that he will not be running my payroll, so I believe payroll will not overlap between two companies. Am I correct?
5. He mentioned, he will give relieving letter and experience letter with the future date(after 5 months, whenever I give resignation). Will this create any problem in my future green card?

Note: I have 14 months left in my 6 year visa tenure

Thanks in advance!