ILR after DL 6 years (set O)

Dear all,
I am writing on behalf of a friend. He is due to apply for ILR on basis of completion of 6 years in UK. We are aware he does not need LIUK and B1 English under DL route. However he has taken LIUK test.
There are two issues.

1. He was granted DL as he entered UK as an illegal entrant but later married a British. They are still married and wife is supporting with his application. But they are living at different permanent addresses due to work requirements. does he need to submit any docuements with regard to his wife or a letter from her and will it be a concern they have separate addresses ?

2. On SET(O) form, section 6.1, about the date of entrance to UK under this category he is applying what date we should put? Is it the date he was issued his first valid visa(DL) or the date he enters UK illegally? (He never left UK since)

Also advice on what supporting docuements he need would be helpful.

Your immediate attention would be much appreciated. Thank you for your time.

Some advice would be very helpful.... Thanks