As I see it, tank fuel is required if you want to reach your destination. As soon as you can, apply Gravity Fuel Feed procedure with the X-Feed OFF. You then get even fuel burn from each wing.
If you get stuck down at FL 150 because of your FL when the pumps fail, you will have to land somewhere and get it fixed.
Or would you climb above FL 300 using one wing tank and X-FEED ON, wait 30 minutes, and then Gravity feed on the failed side? Imbalance might be 1500 kg?
Depends on planned landing fuel... Because it would be irresponsible to deliberately run a tank dry.