Is it safe to take 5v draw from a PC power supply on both a molex connector as well as 5v off of the motherboard on the same device and combine them to power a device needing more energy?

It is generally not recommended to combine 5V draws from different sources, such as a Molex connector and the motherboard, as this can create ground loops or potential differences that may damage components. Each power source may have different current limits and protections, which can lead to instability or overheating. If you need to power a device requiring more energy, it's safer to use a single, appropriately rated power supply or a dedicated power source designed for that purpose. Always ensure that the total current draw does not exceed the rating of the power sources being used.