I know this post is too late for the question, but I thought posting my solutions may help for people who have the arrow problem. My solutions are either i) Line with Arrow or ii) Line with Marker + At extremities. Probably, the second solution is the one he wanted.
After converting symbology to representation, follow below steps.
In the Representations Layer properties,
1. Add a new marker layer - after adding it, it will show 'Marker' and 'Along line' boxes.
2. Click a black arrowhead in Along line.
3. In 'Marker Placements', select 'At extremities' and change 'Extremity' value to 'Both' or 'Just begin' or 'Just end'.
4. For arrow head, click black square marker in Marker box. It will show 'Representation Marker Selector'.
5. In 'Representation Marker Selector', select 'Triangle' and then, click 'Properties...'. It will pop up the 'Marker Editor'.
6. Change angle of the Triangle marker and click OK.
I think Representation is very complex tool, but it is also versatile so you will need to explore the representation tool. I hope this helps.