Another way that i could have prevented this was to make sure we had adequate heating in the property.

Some cities will not even allow us to expand a driveway or add extra parking to the more than adequate front lawn.Then again we inherited a duplex that had parking on the block behind the home.

To answer your question directly my advice is don't jump into deep water without adequate life preservers.

On one hand I want to suggest looking into opening a HELOC on your current home rather than selling, this will give you access to some capital for your down payment funds on your next purchase and not require you to move into a rental for a short amount of time as you transition (something i'm guessing wouldn't be extremely fun especially with a little one either on the way or just arrived).Once you have adequate down payment funds, you could simply watch for the right thing to come along from the comfort of your own home.

As I am shopping for insurance, I can't help but ask myself, "what is adequate coverage for my owner occupied, 3 family home?".

It is providing society with a much needed service, providing safe, clean,  and adequate housing, emphasis on ," SAFE".I would also check with your local building department for what might be considered code violations.

Also If you dont make an adequate payment each quarter(25% of either of those two amounts from above) you will have an underpayment penalty. 

If you are leveraged, one should have adequate reserves. 

My biggest concern in your description is adequately accounting for the capex on the house.

Just make sure you keep adequate records, and take advantage of the deductions this year.