It's too bad you got a UA agent that doesn't know their own rules on open jaws:
"Open jaw: Legal open jaws (open jaw length shorter than flown flight segment length) are permitted. No stopovers are permitted."
also appears on UA's star alliance reward chart at:
http://www.united.com/ual/asset/Star...d_chart_v2.pdf
You might phone UA back and ask them to change this based on the incorrect info provided by the agent . . .
Sorry can't help with the other question. Good luck!