Low pressure on the fuel line could have also been caused by the Fuel Pressure Regulator being faulty, which is a common problem on VX's. A relatively easy replacement cost/procedure too. Irregular fuel pressures from a faulty FPR could have also caused the low voltage readings responsible for the codes you were getting from the O2 sensors.

I don't know exactly what goes wrong with the stock FPR's on VX's, but given the mileage on the one you purchased, it's likely that the original is still in place, so it would be a likely place to start.

Congrats on the purchase, and welcome to the site.