Didn't notice your other post. For clarity I think the rules are the CL rules but I've not checked. From a quick glance your position at the end will be determined by away goals between you and your rival, from what you've said that appears to favour him.
I can't definitively say what the position is or what's used prior to the completion ofthe group because the rules quoted state they are applied "If two or more teams are equal on points on completion of the group matches,...."
So your position currently reflects the rules as intended.....imo. If I was forced to give an opinion I'd guess they apply pts then gd for pre-completion rounds until 2 teams vying for a qualification spot have the same points tally.....then the rules quoted kicks in.