First you nozzles need to have a offset as center is 0,0 for deltas. So 9/-9 mm x offsset might be correct from your description.
Then with 2 nozzles all the nice autoleveling is not very usable any more. The bed must have the same horizontal tilt your extruder has or one of the nozzles always scrapes over bed/printed parts. So ideally both are exactly horizontal. Autoleveling then only allows for very minor corrections that won't hurt extruders or in y direction if they are in x direction. So solution is to level both hardware side same direction and make sure the unused extruder is clean with no ooze dropping out.