Oh I see. I've never considered using crosstrack on the CDI as the RNP integrity alerting is triggered off the RNP value entered in the PROG page. The crosstrack on the map display is an indication of where the airplane thinks it is in relation to the calculated track. The EPE of the airplane is a calculation of how accurate that track is. Two separate things.
I'm not sure about 4 and 5, but RNP 10 oceanic airspace does not require RNP alerting. Non-GPS equipment is certified for various periods of time from their last alignment or DME update. Airbus FMGC use a more or less linear formula in non-gps airplanes to increase the EPE once IRS only navigation begins, but the values have no connection to how the kit is actually performing. As long as you don't exceed the time you're good to go.
Sorry I couldn't be more help.