Hi! Congrats!
I only just did this in November/December so its' pretty fresh, but anyone else please feel free to correct me if my information is wrong.
The most important thing here is this: "When it asks on the online application how long I've been in the UK I put 4 years and 11 months. Is it a problem that it is less than 5 years? I've seen somewhere online that people say to wait to do your biometrics until after the 5 year mark. Is there any accuracy to that?"
YES! You have to have been here the full five years before you can apply.
Here is my comprehensive list of what I put in my application.
Scan of your current passport
Scan of your sponsor's passport/ID
Last time I checked you also needed to provide scans of your previous passports if you have any.
Scan of your current BRP
Signed sponsor's declaration
Proof of pass for Life in the UK test. Your ref should be enough.
I also submitted part 1 & 2 of the 'consent to checks form' but I had those from previous visas and do not know if the are still relevant. I submitted them anyway.
at least 6 months of bank statements (I always submit 7 also) proving that you meet the financial requirement. These should only come from the sponsor (either yourself or your partner, whoever is sponsoring you).
You will also need an employer letter from said persons' job confirming that they work there and make that salary, and the matching month's worth of payslips. The employer letter should be dated no more than 28 days before the application date (the online application)
For good measure I also submitted my sponsor's job contract, their latest p60 and a letter from their payroll confirming the payslips are genuine, as they were only digital.
Current tenancy/housing documents
latest council tax bill
6 items of original mail under join names spread evenly over the last two years from at least three different sources.
marriage certificate
You listed several of these in your list, I just added a few things I submitted with mine. Happy for anyone else to chime in and add more/correct me on mistakes. But I just submitted mine in December and got approved in February and these are the exact documents I submitted.
I entered the reference number as part of the application. Do I need to submit a screenshot of the email as well?
Keep the screenshot handy but I doubt you will need it if you provide the number they send you.
As part of the online application we were asked what the source was and I entered it there. Do we need to draft a seperate letter detailing the source or does that count as the declaration? Also do we need to specify that it's immediately available? It's a regular savings account.
Is it okay if our most recent bank statement is from the same day that we apply?
I can't answer this bit as I never declared savings as part of my application. I always got my bank statements printed and stamped as close to the date as I could.
Best of luck to you!