retain right of residence: desperately need help

hi respected board members and guest,

well, i am from pakistan and i am married with EU member 1-05-2012. we married in cyprus.
we moved to UK january 2014..
since the first day we are living together for five years,
now our relationships is destroyed . we are on divorce/seperation level.
since 2014 we are in uk , we are living together and she is still working legally and taking treaty rights.there are no gaps..
my question are :
what kind of documents do i need to apply for Retain right of residence?
how long does home office took to decide my case?
in case of refusal do i have right of appeal?
how many percentage chances do i have to get ROR ?
does Brexit can effect my case ?
do i still in old law?
i got all her payslips,job letters,council tax letters,tv licence ,internet etc are on our names,
i am really too scared and depressed.

please help me in this matter,
it would be grateful.
have a good day and be happy...