I see. I think if moving 50 steps is unpredictable (backlash aside) then you're going to struggle with autofocus in general, as all the algorithms assume some sort of predictability in the focuser. Maybe somebody else on here with an Olympus may have some tricks.
You can control the backlash movement by setting the backlash amount. When changing direction, the focuser will add this to the previously calculated movement. So you try playing around with this.
That said... what you were initially trying, the Linear algorithm, might be your best hope as it uses heuristics on the second past to try to stop at the best place rather than moving straight to a pre-calculated point.