Should I inform management (read the top bosses) that the job is no longer financially feasible and that I am actively looking for other work?

Go ahead

No, that's the worst you can do

@retoor Do explain

If money is the only reason that you are looking for another job and if you think that there is a chance that they will give you a raise to stay there, then you could try.

But at the same time, you put yourself at risk of being fired, so you might want to make sure you have an alternative before you let them know that you are looking for an alternative.

Don't know what you mean with that statement.
Is the job not paying enough or is the company not doing well enough to keep your role long term or full time?

@GinjaNinja see @Lensflare comment

Threatening to leave unless you get a raise is unprofessional. Let them know your salary isn’t good enough and ask for more. You don’t need to hide the fact you’re job hunting, but also don’t make it a threat, and you should be within professional conduct.