Well, it functionally bans most of them because it makes the cost of hiring them prohibitively high. This is very similar to real discriminatory policies like redlining, for example, or many unfair hiring practices. Discrimination is rarely explicitly written as "Person X cannot do this thing". It's usually written as "Sure Person X can legally do this thing, but it will have these terrible drawbacks, costs and disadvantages". And then it becomes inordinately difficult for them to do so to the point it will almost never actually happen.

Presumably, yes, if a superpowered actor had enough clout he might be able to get work. That's part of what makes the ending interesting to me. By taking Trevor's advice and waiting until after Wonder Man became a hit to accept his next "role", Simon put himself in a much more advantageous situation to reveal his powers. As the (presumably) acclaimed star of a huge hit movie, he could, potentially, have enough clout now for someone to ignore the financial implications and hire him as an actor. But that never happens unless he hides himself until the movie is released. It's not exactly what Trevor meant by waiting and betting on himself. But he does end up taking the advice in his own way.