Moved from the ILR board to this

The form is very self explanatory but I had a few queries:
1. The asks if the applicant has made any immigration / visa applications to the UK - is this in the lifetime of the applicant or qualifying period?
If lifetime then I assume I’d have to include my husband’s student visas which were beyond 5 years
2. With regard to the referee declaration form, does it have to be a wet signature or can a digital apply ie digital as typed “John Smith”
3. Evidence for proof of residence - the form states that if the applicant does *not* have passport stamps covering the qualifying period then they should submit letters such as P60s etc.
My husband’s qualifying period is the immediate last 3 years, we have passports covering all entry and exit stamps. Is this sufficient / all we need to provide for proof of residence or should we include P60s etc?
4. If we have to include proof of residence in the form of letters, is it the same as what I’ve gone through with ILR, ie a good spread over 3 years?
Thank you