I think our courts would find a $600+ charge to be excessive.

Seems excessive to me.

Just know no matter how much planning you do, you will be making endless runs back and forth, almost every day, and it is what it is my friend- BUY MORE THAN YOU NEED and then return all the excess all at once using the card(s) you bought it on at the end of the rehab.

I was looking at those two formulas and thinking to myself this seems a bit excessive for rental property investing, thanks @Bjorn Ahlblad! 

You can get an Excess or Umbrella policy that provides additional coverage. 

When a tenant moves out, transfer the deposit back to Checking so it's ready to apply towards expenses or refund the Tenant.If you end up with excess funds in the Checking account, I recommend you transfer it to a third account designated explicitly for future investments.

Buying out of state is fine you will only have an issue if you go with a lender with overlays or requires landlord seasoning.They may question your ability to manage the property if you are out of state in terms of excessive mileage away.

No issues with shower windows, in fact the window can be a benefit to excessive moisture and potentially mold.

If it 'fails' or would be excessively expensive to repair, you can just back out at that point and forfeit your EMD.

If there were any excess rental loss (not used up in 2019), can it be carried forward to 2020?