Before I could get the appraisal appointment scheduled, the snow started to melt and the freeze/thaw of all that water caused a leak in my unit. 

I've contacted Cozy customer support explained situation and requested freeze and investigation before turning money back over to tenant.  

With that said you need to make a significant improvement on the property for the BRRRR otherwise the cost of getting that equity back out can put it well over 10% (and you are just taking it out to invest in a 7 cap), which means its cheaper to not refinance in the end and leave the equity in the rental.You can typically lock a rate with a HELOC after you a balance on it you can "freeze" that balance at a rate. 

The other option is to leave it without any heat as long as its getting residual heat from the basement and other units there is no reason to heat that area unless there is a potential of freezing pipes that may run up that part of the building to the second floor. 

if it is the problem is going to be that even if you seal this side up, you've got an access point for water that will fill up the wall and freeze in the winter.   

What they can do is Freeze a HELOC from further withdrawals or lower the available unused limit if something crazy happens like it did in 08 where equity evaporated. 

I could carry it all into the basement of the property, where it will be closer to the heater and stay above freezing.

That law allows the landlord five days to remedy the failure after receiving written notice or the tenant has the right to terminate the lease.A few thoughts on heat.  1) you want heat restored ASAP because if it gets too cold it freezes your water pipes and you have bigger issues. 2) You can provide temporary heat in the form of space heaters.

I also noticed you didn't use the RE Cashflow as an income in your calculation or may be its hiding in one of your formula.In any case, I am numbers guy too and sometimes I get lost in it and get to brain freeze mode.

The only immediate response they ever need is when the place is flooding, on fire, or there's zero heat on a freezing day (or depending on state, AC is required).