The text is merely a transfer of the letters in Hebrew. In Chayei Sarah his name is M'lud (מלוד). In VaYeishev his name is written Molad (מולד).
Although there is nothing in this source to indicate why the change of letter arrangement, just considering the meaning of the words could be an indication.
M'lod means literally From Lud. Lud is a city-state in Asia Minor which is mentioned in Pesachim 50a in connection with the concept of Mesirut Nefesh. It would be in what is modern day Turkey. At the end of parshat Chayei Sarah in Sefer HaYashar it indicates that the children of Avraham and Keturah moved to Asia Minor. In particular, sacrificing ones life at the hands of the government for the preservation of the community as a whole, as described there, is a highly meritorious act.
Molad has several meanings such as new moon and hard labor. But in this context, it also has a plain meaning of descendent. His merit derives from Avraham and his second wife, Keturah.
There may be mention in another midrashic source about the particular meritorious act of the father of Merusha that accounted for his name change.