may i use the global oe pin as the global reset pin?

Unlike global reset, global OE isn't said to have dedicated routing resources. Thus a GCLK input would be the preferred source to minimize routing effort with your second reset input. I don't expect timing issues with a global reset, normally. If unrelated to the system clock, it should be synchronized for safe reset behaviour anyway (a feature, that can't be achieved with the dedicated global reset input, by the way).