Hello Mykeris,
Hum, do you feel satisfied with the fickle opinion from the museum "expert" who first said that it is a replica and then a genuine antique piece? Is he a specialist of the antique Buddha/ Hindu period in Indonesia and did he give you some valid reasons for changing his mind in this way? Are wayang motifs on a blade made during archaic Buddha period realistic?
If I were in your place I would not give too much confidence in his assessment.
Regards