White powdery mold on Lomo after opening?

No Not dangerous. White mold is fine. Black or slimey is bad.
If you wish to prevent mold ,vac seal, No Oxygen, Mold will not grow

Also, does it hurt to let the Lomo continue to dry past the 35% moisture loss target goal? How far can you dry it and it still be usable?

42% is wonderful, if the outside is drier than the center, vac seal and refrigerate for a month or 2. The moisture will equalize and the flavor will improve. 🙂