Regarding the genetic data, I would create these priorities.
Try to get everyone in your mother's generation and older to test. This may be a challenge since your mother seems to be hiding something. Hiding or denying Jewish roots did occur although you do not know for sure this is the case here.
Upload your DNA to FamilyTreeDNA, MyHeritage and GEDmatch. All are free and GEDmatch has the best tools.
Contact everyone closer than and including third cousins. If you are lucky, one in four will respond.
