Later that day, I am at 75% again and repeat the process two more times (roughly 1550-1600 mAh for the next two times) and then I am stuck with TWO glowing lights on the power bank

You can not charge this, and another device at the same time (daisy chain a charger).While charging a device LED lights are always on, if you turn them off, the charging stops, and they are bright.

If the power bank shows TWO glowing lights, then the charge states that it's between 25 - 50%

There is 4 led light that provides you a status of battery life on this power bank.

When in fact the math shows that it should show 3 glowing lights (roughly at 72.5%)

The led lights are visible during charging and show how much power is currently in the power bank

11,600/16,000 mAH is 72.5% which means the power bank should show 3 glowing lights, not two

After reaching a 100%, I am left with THREE glowing lights on the power bank (should be roughly 725-800 mAH).4

For Output #2, the ON/OFF Power switch and blue LED status lights function as stated in the enclosed instructions