How to take 6 months sabbatical while on H1B/Greencard

Hi,

I have an H1B and I'm currently on my 4th year of working in the US. i,e it is valid for a total of 35 months more before the 6 year period ends. I am looking to take a 6 month sabbatical, mostly during the last year of my H1B and will ask the company for a leave of absence for 6 months but plan to come back and resume working.

I also have the option of asking my company to file for my Greencard now but I want to understand how H1B/greencard will be effected by this sabbatical outside the US. I have listed some questions below but ultimately am looking to find out what the best solution is for achieving the 6 month sabbatical

So my questions are

1) Is it possible to take a sabbatical and travel outside the US for 6 months while retaining the H1B with the company, even though the company isn't going to pay me but I am listed as their employee and they intend to resume my salary when I rejoin

2) Will the above effect my greencard process, because I will effectively be coming back with 6 months left on my H1B and I will then start my greencard (I assume that the time I spent outside the US will not count towards my 6 year H1B duration)

3) If I start the Greencard process now, then will I still be able to take a sabbatical at some point once the greencard application has reached some stage? 

4) If I leave the company and the country and then after 6 months apply for an H1B from outside the US to come back, then will I be subject to the quota system or will I be considered in the visa transfer category, i.e I don't have to worry about the cap or waiting till October etc.

Thanks so much and appreciate the answers,

Sid