Most decent parents would be doing all they could to run a man like this off so the 16 year old has a chance to grow up and get some life experience before settling down and starting a family.
I agree with this 100% BUT it's only relatively recently ( in history) that women have tended to marry their men their own age. In the past it was very common for women to seek out an older, wealthier and more experienced man as a husband. The difference was they married them. Obviously with the emancipation of women , being a woman in 2018 is very different from 1818 or 1918, but in those eras women often sought out men who were established in their careers, in order to benefit from their assets.
The difference with that and the OP is that in the past people would marry because illigitimacy was stigmatised and divorce was rare. Yes, women would exist in unhappy marriages, as they had no choice, but few if they were married would end up homeless.
The OP fell halfway into that construct- uneducated, unable to support herself, but lived with a man, which provided no security.
I don't think it is fair to say ALL age gap relationships are wrong. It depends on the two people involved. For some women, who meet a man of 30 when they are 16 and get married when they are 18 or 19, it could have a happy ending. (A classic example of where it didn't go right was Charles and Diana- same age gap, married at just 20... but that was doomed for all kinds of reasons.)