This is often easier in lower tier markets where the appraisals are not indicative of how the property would sell in an arms length transaction.The other risk you run is over extension.

When there is no court involved there is no case number (that's a simple indicator to look for in a notice if you have not researched the details of the property code) so you have to look elsewhere, but, where and what to look for?

The plumber’s report indicates that the leak may have been caused by an overflowing tub or sink upstairs, but the tenant in that bedroom denies any such incident.As a result, I now have substantial expenses for the plumber and restoration company, including drywall repairs, painting, texturing, and reinstalling electricals.

Indicative price around $1.1M, which would be a loss, with tax around 2% potentially 20k/year.

Since this is a long-term investment, it’s still important to prioritize areas with strong population growth and a healthy job market—both are great indicators of long-term potential.

Is their current portfolio distressed, or was the majority of their current portfolio purchased at the peak of the market, indicating that they might be in distress in the near future. 

you will need to look at the APN of the property and line it up with what you actaully bought. as mentioned the tax assessed value is not an indicator of value. the land could be a utility easement, used for stormwater management etc.

What I don’t understand is how to overlay all of that information to pick a good spot and I also don’t understand the appropriate thresholds for each of those indices (income, percentage in the target age group, and how dense).

Look for ownership name in LLC and address's other than property, these 2 things are very good indicators it's a rental property. 

I guess I'm not as keen nor experienced enough in knowing if they will be able to EXIT future deals now because they have only proven it once which isn't a long track record at all... it maybe is a future indicator of their inability to BRRRR for their LP investors.