We didn't go savings route but here is my checklist. From your list I think you need photos and communication proof. The wise elders on this side can give you more help obviously.but mine got approved!
Table of contents
a. Current Passport
b. Any Expired Passport
d. 2 passport sized photos of applicant
1. Application and Receipts
a. Application-
b. Appendix-
c. Biometrics Stamped Receipt
d. IHS Payment Receipt and Confirmation Receipt
e. Letter of Introduction
f. Letter of Sponsorship
g. Copy of Sponsor’s passport page
j. Flight Itinerary
k. Extra Return Shipping Label
2. Financial Requirement – (so proof of savings held for 6 or more months with no dropping below minimum requirement
3. Accommodation(may differ depending on what you are doing but must show what is going on we did staying with family)
a. Letter of Invitation from Sponsor’s Parents to Live at Property
b. Land Registry
c. Land Lease
e. Mortgage Statement
4. Proof of Relationship
a. Marriage license(you would add intent to marry information here)
b. Photos
c. Visits to See One Another and Holidays Taken Together( we did fight email confirmations some people do boarding passes)
d. Communication Examples
i. Facebook Messenger
ii. Emails
7. Return Shipping Packaging
8. We only did copies of what we wanted back so that's up to you what you wanted.
You would need to include your divorce decrees as well. And in proof of relationship show intent to marrry so engagement rings, corresponding with register that sort of thing.
What accommodation sre you using. Rental or ownership. If you let us know we can tell you what to send