@Alexander Phillips
Wow, this is a mess and I have so many questions. It is unfortunate that you are in this position and it sounds like you have had very little to no communication from your representation or lender.
I assume this is a 3rd party lender you are using and not the builders lender? I can not fathom how you were not informed that this was a DSCR loan and you should absolutely inquire about the specifics such as whether your are IO or not and the pre payment penalty. 8.4% is high in todays rate environment, even for DSCR.
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. This is improper communication and expectation setting.
Why is the listing agent putting tenants in the property and why are you communicating with them, do you not have your own representation? Are the leases even valid, if they are not signed by you or your property manager?
Your options are going to come down to what your purchase agreement says. Odds are you will lose your EMD if you back out, which may be a better option than sticking with this deal (depending on the amount and how it impacts you financially.) If you have a financing contingency in place, that could have been your scape goat when the DSCR ratio no longer worked.
More than happy to review any documents you have an offer any advice I can if you shoot me a message.