Use Non-Comptete contract to get here way.

I have a very serious situation with my employer. My current client is offering me to join as a permanent employee and i am facing the problem:

My H1B emplyer and a middle layer have a non-comptete contract with me defining not to join in any circumsatnces, and only work within this chain. They are using this as a fist to get a away with there demands when it comes to negotiating salary or anything. Are these contracts legal enough to enable unethical practices by these consulting companies to people with H1B?
Also, my current client is offering me to join them if my Labor is approved which i have recently started with my H1B employer, is it possible to get a approved labor for IT from another company? Appreciate all the inputs.
Thank you