There is more fuel efficient way to get to Mercury - by using gravity assistance from other celestial bodies. Main option is to use Venus - it is the easiest one to perform. But you can also use Mars assistance first, before Venus, or entirely without Venus (no benefit here, but still doable, just for fun), it might be easier for you to get to Mercury with best trajectory this way. Directly from Earth to Venus it is easier of course, but it is still not obvious how to get best trajectory, while bad trajectory requires much more fuel to burn.
The good news are - you have a lot of extra fuel, thus you can afford bad trajectories as long as gravity assists were used at all.
And in addition to that you can also use Mercury's assistance as well to reduce differences in speed between you and Mercury, which will allow using less fuel for slowing down before landing.
With best trajectories on each step you will still have 15%-20% of fuel left after you landed.