Married- Separated

hello,
i need to apply for UK visa, i am married, separated from my wife since last 1 year, but since it is not a legal separation, I do not have any documents related to our separation. I have our marriage certificate.
In the visa form, there is an option to mention marital status as separated.
My questions are:
1. Do I need to provide any documents when I claim to be separated? I do not have any.
2. Will i need to give any declaration to this effect? If yes, what sort of? My wife will not help me and will not sign or provide any documents.
3. Or shall I mark myself as married, avoiding showing separated!
4. Will my marital status have any effect on my granting of visa? I shall be applying for Business and subsequently Tier-2 Visa.

Thanks and regards

SD