The problem is that employers and prospective employees will disagree about what is and isn't "misinformation", and only a trial can resolve that question when the law gives a cause of action for it.

Sure, but the threat of having to spend money on a trial should incentivize employers to be factual and clear in their advertisements. Edge cases will get sorted out by trials at first, but then there will be case law that will discourage people from bringing questionable cases.

Again, this starts with a proposal to end "ghost jobs" and ends with... whatever problem it is you're trying to solve here. And doesn't fix the "ghost job" problem!