Immigrationboards.com

Before explaining my specific case, I'd like to say that I've read all over and tried to find an answer, but couldn't find one that match to mine.
The Gov website suggest that I can apply after 3 years if my spouse is British, but need ILR/PR/Settled/resident card etc so I wanted to ask here if someone can please help me to finally understand.
I'm asking in advance since my employer want me to clarify these things.

I've arrived to UK at January 2015 and work as a permanent employee since then. documents that I hold:
1. NI tax record full year paid for each year (4 for now) as per below (copy paste from HMRC my account)
2018-19 Your record for this year is not available yet
2017-18 Full year
2016-17 Full year
2015-16 Full year
2014-15 Full year

2. P60 records: 2015, 2016, 2017, 2018 and in less than 3 months 2019 (5 total)
3. Proof of address for each year: 2015, 2016, 2017, 2018, 2019 (Utility bills)
4. I allready applied before for Registration certificate and received this document confirming my resident here (not a PR, just registration certificate)
5. My wife and my kids are British (from birth) - not sure if it makes any difference
6. I have Polish passport

- Can I already apply to anything? if so, to what?
- Should I apply for Pre-Settlement at March when the service will be available? or wait till January 2020?
- If I must or should wait until January 2020, then after this date I'll be PR automatically if I apply or else it takes time?
- Considering my circumstances, once I have the PR then I need to wait 1 more year to apply for citizenship even though my spouse and kids are British?

Thanks in advance

You need PR before you can apply for citizenship. PR takes 5 years and you must be a qualified person exercising treaty rights for the whole 5 years.

Once you have PR and the document proving it, you can apply for citizenship immediately based on 3 years as spouse of British citizen.

Thanks! I highly appreciate your help
Can you or someone guide me please how can I be clear when I send my documents that I'm in the UK 5 years?

As mentioned I will have soon 5 x P60/NI documents that I paid.
In terms of Utility bills, I started to have 4 months after I came since I paid rent includes all the bills

So my question really is how can I prove that I'm here from some specific date? or else utility bills from April 2015 will be good enough as a proof that I was here for all time of 2015?

Someone please?

Thanks in advance