One way that you could do this is with a viz in tooltip. In the attached example I have created a second sheet with the account numbers, income, and sum of accounts. I created a viz in tooltip on the map and show this worksheet in the tooltip. It requires an action to filter the table in the tooltip to just the selected accounts.
I hope this helps!
TestAvgIncome-sb.twbx 138.4 KB
Unfortunately, I'm running 10.3, so I don't have this viz in tooltip. However, I was able to find a tutorial elsewhere which shows how to make the map a filter action, so when I select the points, other worksheet data I've dragged in from other sheets onto the dashboard show the summary data. Thank you for the tip. If I update in the future, this will be helpful