Set (O) - income proof

[LondonAegis]

Dear Experts,

Hope everyone is having a good day.

My wife is in the process of completing Set (O) application form to apply for ILR and is currently depend on me. In terms of income,
1) whose income proof is needed - mine or my wife?
2) Is there any criteria, for example, last 3 months income proof or 6 months etc
3) What is the minimum income level?
4) Does savings balance matter?

Many thanks in advance for all the experts and gurus!

Best regards,