Seeking legal advice.

Straight to the point: I want to be paid for my efforts.

I have already put, and will continue putting, large amounts of time into developing a game system, and a game world. I want them to be compelling and enjoyable. This necessitates feedback. Therein lies the rub. How do I expose game mechanics for review, without effectively giving them away for free?

Large corporations do closed testing under non-disclosure agreements. Is this the only safe option? Wizards of the Coast released much of the d20 system as Open Gaming License material, but not until after they'd published a finished product. If I expose my design process here in the name of active critique, what's to stop someone else from taking it and beating me to hard-copy publication? Even worse, possibly doing so with a half-finished and less than streamlined version, so that even if everyone recognizes that I'm the victim of foul play, the first general public opinion is poor, and willingness to try the finished (real) product is decreased.

Short of clamping down and revealing nothing publicly, is there any defense against this possibility?

And what about game world material? That, I think, is slightly better protected by implied copyright; but is there anything simple (and preferably free) that can be done to assert and secure these property rights when publishing on a public forum like this?

I'm hesitant to share much of anything until I know more about these subjects. Pointers would be greatly appreciated.