Spouse Visa Application – A few worries

My fiancée and I are planning to fly to Taiwan (her home country) on 18th January. We’ve arranged a wedding date of 21st January and will apply for a spouse visa ASAP afterwards. I’ll fly back to the UK on 8th February and my new wife will remain in Taiwan for however long the visa process takes.
We’ve been preparing all the documents together and I should have everything like a letter from my landlord, her Life Skills English test pass etc. However, there are a few things that have me worried:

1. I get paid monthly, on about the 24th/25th of the month. My last payslip is dated 25th December. Like many companies these days, the payslips are electronic, so I need a letter from my boss confirming that the print-outs are genuine. He’s happy to provide this, but I won’t be able to get my 25th Jan verified. My boss even agreed he would date the letter later so it covers my next payslip, but I wouldn’t have the bank statement to match up with it, so I don’t think that’ll help.
   
   Therefore, I’ll need to use my December payslip. The problem here is that from my calculation, our wedding date is 27 days after, so I’d need to apply for the visa on our wedding day or the day after so that we don’t fall foul of the 28-day rule. From reading about this rule, I feel pretty sure it’s from the date of the Online Application and not the Biometrics appointment, but it would be good if someone can confirm this.
   
   Is that completely crazy? Applying for the visa with one day left on the clock?
2. From what I’ve read, it’s fine to apply right after being married, so long as you have decent evidence of the relationship beforehand. We’ve been together for 18 months, spent Christmas together for the last two years, have lots of photos, emails and tickets from 13 trips to see each other (she was a student in Belgium, not Taiwan at the time!), chat logs etc. so I feel we’ll have enough.
   
   However, we will also have a very simple wedding. In Taiwan the wedding is a purely legal thing that happens in an office. There won’t be guests, invitations, dresses etc. It’s traditional to hold a banquet later on, often weeks or months later. We’re actually planning to do something in 2020, to spread the visa costs. I heard someone from Japan ask something similar online as they were assured it would be ok.
   
   I feel a bit concerned that we’re applying so soon after being married AND the wedding itself will be extremely simple – will they suspect us too much?
3. With my pay, there was an issue where I was on emergency tax for about 3 months. I chased them on this at work and because they owed me so much, they gave me an ad-hoc payment immediately and then reclaimed it from HMRC. Is it worth explaining this, or getting my manager to do so?
4. I have been married previously – separated before the relationship began but only got my Decree Absolute last April. Do I need to provide any evidence, and if so, what?

Apologies that this is a bit long. Any responses are appreciated!