A scammer pretending to be “Stranger Things” star Dacre Montgomery turned a single mom’s world upside down. McKayla was estranged from her “toxic” ex-husband, and “Dacre” claimed Montgomery’s real model girlfriend Liv Pollock controlled their joint finances. In total, McKayla said she sent “Dacre” about “10 thousand-ish dollars.” The real Montgomery reportedly makes more than $100,000 per “Stranger Things” episode. …