Would you happen to have any resources for an amateur screenwriter looking to have a script critiqued? Without the chance of having the idea being poached?

writerlyn:

For one thing, I would like to yell to the tree tops that it is very unlikely that it will be poached.  Very.

If you’re really worried, register it with the WGA.

Then from there, contact other writers, contact professors, contact anyone you know, have them give it a read and critique.

Shouting in harmony. But registering it is cheap.

https://austinfilmfestival.com/submit/coverage-program/

Austin does a good, amateur-writer-friendly coverage program for $100.