British Citizenship - Proof of Residence

Hi,

I'd be really grateful if someone could kindly help confirm a few questions I had around proof of residence in the UK and trips outside the UK. To clarify, I'm an EU citizen and am applying for settled status now, so do let me know if I'm also missing any requirements for settled status.

1) If I just submit an employment letter for each year in the last 5 years, will this be enough for HO? I'm a bit concerned - I don't really have P60 for every year because some of the "jobs" were essentially unpaid internships (I think on a volunteer basis), so could I also submit a letter confirming volunteering? How does the HO go about checking this (just concerned given not all roles were on a paid basis so don't want it to raise any flags)?

2) Given I may not have P60, do I need to show I was self-sufficient or anything, either for the settled status or citizenship? How do I prove this? I heard insurance might be needed + some sort of proof I wouldn't be a burden on the system? I had family looking after me at this time so not sure how to prove this

3) Trips outside the UK - I filed a request for this data, but it seems to be incomplete, as I often exited by car/with my national ID from the UK. I'm just concerned because I'm not entirely sure how the HO checks - anyone know? Don't want them to have missing data and then simply say that what I submitted was wrong

Thanks!