Certainly worth getting the alignment checked again imo. Find someone with Hunter 4 wheel alignment if you can.
Could be that somethings also been damaged/worn by the pot hole so some investigation work underneath required.
Check right across the tyres also to make sure there's no uneven wear.
Like above - splitter not required, especially as you said it didn't do it when you collected (and it won't help anyway!).
Road surfaces and cambers play a huge part in grip levels as well so maybe collect more data on different surfaces.
Commonly noted that Haldex oil service and filter clean should be carried out more regularly than VW state in their service schedule, the filters are prone for getting clogged, pumps can get damaged and costs spiral. I do mine yearly with the car service (12k a year). Expect around £100 for a specialist but always ensure the filter is removed and cleaned!
Could always test the effectiveness of the Haldex with a little launch...... 🚙💨