seanpham

NVC takes the last date when you submitted the main documents.  PCC is one of the main document.  In your case it is Dec 6th.   You will get it reviewed later this week.

Where are you in the process? Is your case at the embassy and awaiting an interview or are you just now getting started?

What matters is your current income. If your current income is subsubstantially higher, your capital doesn't even come into play.

Does your current earned income suffice to meet the requirements or are you also using investment income?

The capital loss will reduce your taxable  earned income by $1500 or $3000 depending on your filing status.  And no they will not ask about it, in my experience. I’ve had a net capital loss carry over for years and no one from State or USCIS has ever asked about it.  
 
As an aside, please read up on John Bogle
 

@Mike E is correct. There are ways to use a capital loss to your advantage, tax-wise. As with everything tax-related, how to do this depends on your specific situation.
 
This is an example of how my husband and I managed our capital losses this year to lower our tax bill next year: https://www.bogleheads.org/wiki/Tax_loss_harvesting
 
The Bogleheads site also has an excellent forum focused on investing.
 
To return to @seanpham 's original question, USCIS and DoS are concerned with your current earned income. As long as you can demonstrate you are consistently earning enough to meet the requirements, you will be fine.

Agreed with all that but  the point is that because  current earned income is more than sufficient for I-864 purposes, reducing that current income by $3000, which is what will happen in 2022, makes no difference to the decision by a CO.  

You don't need to provide any info on any such things. Income is the king. One can even have all of his income spent on mortgage/loan payment with $50 per month savings and still qualify. All you need to have is good income.

The answer to your question depends actual circumstances.  If you are self employed, and the "loss" impacts the total income line of your 1040, then that's a problem, in that it will make your current income negative.  If it only impacts your assets, and not your "total income" from your tax return, then no problem.  Please clarify.

She can print and sign her intent letter and scan it for you to print out.

It will be denied, but hopefully in the form of an RFE so that you can fix it.

You will receive and RFE for the missing signature.  Have another one prepared and ready to be sent. 

Automatic rejection.  There is very little chance it will be accepted.  Even if it gets by USCIS, NVC can still send it back to them.  

The I-129F has only a few required documents:
 
- Evidence that the petitioner is a US citizen
- Evidence that the petitioner and beneficiary met at least once in the last 2 years
- Evidence that the petitioner and beneficiary intend to marry within 90 days after arriving on the K1 visa
 
Any other attachments or documents are not required (other than divorce certificates if previously married) and are only for "front loading" for the destination embassy.
 
As a key requirement, yes, an RFE would be sent for the missing signed intent letter.  You may be able to contact USCIS and see how to send one now to be added to your petition.

Ordinarily I would advise doing all you can to meet up in a third country, get married there, then file for the spousal visa, but it's not worth it if there is a high chance that your fiancee could be stranded abroad indefinitely at great expense.
 
A K1 may make more sense in your situation.

If I could go back and do the CR with my wife I would but, every couple's situation and desires are different.  Is there a neighbor country if Vietnam that both of you can travel to and get married if you decided to go the CR1 route?  
 
As mentioned before with your 2 year meeting requirement coming real close, you could file now and should if you decide that route. 

Overall, the CR1 is a more superior visa, but of course there is the challenge of getting somewhere where you can both get married.  Generally, I would recommend finding a way to work out the spousal visa (CR1), but with your two years of in person meeting coming close to an end, I would suggest filing the I129F as soon as you can.  If things change, you can always make changes yourself.
 
Good Luck!