But given that it expressly includes a specific performance provision I would not be ignoring it… and neither would a judge or mediator.Real estate is unique by nature.

Furthermore you can vastly increase your returns through leverage using a non-recourse loan but that will definitely trigger UBIT but again the numbers can still make a lot of sense. 

Naturally, there is a higher return with higher risk and vice versa.

I did most everything I was supposed to do, increase my income, decrease my living expenses, save cash, etc.. 

My guess solely looking at your numbers is that it's an older/distressed property which means you have to account for more costs in capex. 2nd thought being it's not in the best of neighborhood then you'd have to take into consideration lower quality tenants/ neighbors and maybe increase expected vacancy and late payments.

Buying more properties, if buying correctly, simply does NOT increase your DTI or at least in my example above much at all. 

Death Rate: The death rate has been gradually increasing.

Without actually building the 3rd unit, would this new triplex eligibility increase my property's value? 

They had an unfinished space counted as finished space increasing the size of the home by ~10%.

Just make sure you are saving towards those slow months during the peak months, buy a deal at the right price (don't overpay just because its a turnkey STR or you think it will make more money than projected), and look into ways to increase bookings during those slow months with some marketing and operation tweaks.