Welcome to the forum
.
We seem to be in a special situation. I am an American and my wife is a dual citizen US/UK, but has never lived in the UK. We both currently live together in Chicago, she is going to London this week to look for a job.
As far as I can tell, you're not in a special situation at all - your situation is very common and doesn't seem any different from anyone else's here
.
I have a couple questions: 
Does she need to have a National Insurance Number to apply for the spouse visa?
Will there be an visa interview?
When do you get biometrics?
1. No, I don't believe she needs an NI number for the visa. The application form may ask for it, but she can just put something like 'N/A' or 'sponsor has never lived in the UK'
2. No, there won't be a visa interview. Everything is done by post/email (you will be in Chicago, while they will have your documents and processing the visa in Sheffield, UK)
3. You do biometrics after submitting the online visa application (and paying for it), but before mailing your documents to Sheffield for processing. When you apply online, you will be prompted to make a biometrics appointment at a local USCIS center in Chicago (or wherever you choose to go for it). You will need to get the documents to Sheffield within 14 days of the biometrics and no more than 30 days from applying online. The date you apply online and pay for the visa will be your official application date
Wife will create a cover letter stating:
- type of visa applied for
- list of documents included
This is not quite right. It's the US citizen who writes a basic (optional) cover letter stating what visa is being applied for, a list of documents and any explanation regarding the documents.
The UK citizen must instead write a mandatory 'Letter of Confirmation/Support' for the visa, which includes:
- her ability to sponsor a visa (her UK citizenship)
- her employment status and how she meets the financial requirement
- where you will live in the UK
- a short (brief) history of your relationship
- a list of the documents she is including in support of your application
A sample Letter of Confirmation can be found here:
http://www.londonelegance.com/transpondia/sites/default/files/spousal.pdfIn regards to the rest of your documents, they look pretty good overall, but just a couple of things:
My Info (US Citizen)
• resumé/CV
• prepaid UPS Express packaging for return service
- Take out your CV/resume. It will not be considered for the visa (they are not allowed to consider it) and so is unnecessary.
- You won't be able to include 'prepaid' packaging for return of your visa because there will be no way of knowing what weight it will be, when it will be shipped or how much it will cost yet. Instead, you need to register an online account with either FedEx or UPS (most people here use FedEx) and then set up an international waybill for return of documents, which your account will be billed for when it is used.
Wife's Info (UK/US Citizen)
• letter of sponsorship (is this a SU07?)
No, the SU07 is not required for a spousal visa (it's only for 'special case' visas such as elderly dependant relatives or adult dependant relatives).
The letter of sponsorship is what I mentioned above (you write the cover letter, she writes the sponsorship letter)
Marriage/Relationship Evidence
• wedding photos
• a few photos of us together
- Only include 1-2 photos in total. Maybe one from your wedding and one of you together at another time.
- You might also want to include evidence that you have been living together in the US... such as a couple of utility bills, a tax return, or a rental agreement/mortgage etc. Normally, if you hadn't been living together you would need to prove regular contact while living apart (i.e. if she was in the UK and you were in the US).
