Also, if you have limited or no history of rental income, you'll have to get an appraisal on the departing home to document you have at least 25% equity in the home.

However this leads to challenge 2, I'm not sure that the actual appraised value is 13.3m, it is likely, imo, closer to 12m.

How long can/should I wait for the appraised value to change, and will it go up or down?

I should hopefully have an independent appraisal  within the next few days.HELOC will be from primary residence. 

You’ll need to provide documentation such as income verification, credit history, and possibly a property appraisal.

Unless the appraisal literally just came in before closing, you should not be informed this late into the process that the DSCR ratio does not work.

How does the appraiser and lender view this?

I had the house independently appraised for 410k and offered 385k.

Here is some info on that as for"skin in the game".Gift funds are acceptable as 100% down payment for loans <75% LTV/CLTV Gift funds are acceptable for loans >=75% LTV/CLTV; however, the underlying Borrower(s) must contribute at least5% of the transaction (lower of Purchase Price or Appraised Value) from their own fundso Example: A $500,000 purchase price where the LTV/CLTV is going to be 75% or higher would require the borrower to have a $25,000 of their own funds provided ($500,000 x .05% = $25,000)

And what did the property appraise for currently?