5yr residency

[sally1]

Hi
I am nearing my 5 yrs in the UK and have ILR based on marriage to British Citizen

I want to apply for Natrulisation on the basis of 5 yr residency as although we are still living together (for the kids) he will not help with this issue

I am unable to get marriage papers of him and cannot obtain further copies (foreign marriage) so 5 yrs residency route seems my best option. My questions are

1. How do i word my application so it is dealt with on the 5 yr residency?

2. Will this raise any issues with the HO? as to why this route?

3. Is it better to use a lawyer/solicitor?

Thank you and god bless