Extension of Tier 2

Guys,

Few Questions about extension. I got my tier 2 in Oct 2012 and it is valid till 15 October 2015 however I am quite eager to extend it as soon as possible but also want to have it for as long as I can so that i have a very comfortable amount of window to apply for ILR. So questions are as follows

a- I am planning to Apply in April or May is 1 June a good work start date to be put by my employer?
b- Can my employer put end date as Oct 2018 so that in that way my 6 years will also be completed at taht time and end date is same as well so no matter whicever date homeofffice picks it will be till 1 october 2018?
c- If my employer puts Oct 2018 does it meeds i need to pay under the category of "more than 3 years"?
d- What happens if my employer puts Exact 3 years from start date as end date? In that case will my date will be exact 3 years from the start date because home office will pick smaller of total six year or work end date?
e- Is there any problem with my approach to get extnesion now till october 2018? The only reason i want it is so that i have more relaxed window to apply for ILR aftr 5 years whenever i cna.

your feedback will be welcomed