Salem has different rules that take precedence over common sense, local laws, federal laws, etc. Just as Stefan's shares were taken from "widow" Gabi and returned to Stefan, his life insurance was claimed by the widow, so is no longer in existence; Social Security ...no problem there, he just did not have a job, so did not pay in. That doesn't cause any problem, just a much lower SS check after you retire.
I do agree about "being married", tho. He was declared legally dead, certificate and all, & I guarantee you, when you claim a person died, you have to produce death certificate. But then, they have made movie comedies, about people with dead spouses finally marrying again, then several years later, the dead spouse turns up. I guess courts decide then what to do.