Can I safely run a server with redundant power supplies off of a standard 15 amp outlet?

For "is this circuit safe" ask an electrician. Seriously, electrical fires are no joke, and some old wiring is terrifying.

Regarding a rough estimate on draw, that's not how redundant power supplies work. Properly sized, each could carry the load of the system if the other failed. For what that load is, make an estimate with component specifications, such as with the HPE Power Advisor tool. That system is closer to 300W. Probably the 460W power supply would be more efficient, oh well.

As you have this hardware, measure yourself. Get metered PDUs, and check what the draw is from each supply.