Walkthroughs for custom maps.

As a result, we stop at cell 137.0, five cells away from the finish. I have no idea where else we can gain a turn.

Perhaps there is an obscure logical trap on the map that recalculates direct and diagonal moves. Although, according to the description, you even took into account the recalculation of moves when opening the hero's window.
P.S. The move count after the oasis has not been recalculated.

– oasis – Mutare Drake (Armageddon) – oasis. We summon the ship from point 31.9 twice to land at point 30.9 (on land, 2991 moves, in water, 9083).