I have the post 9/11. Can I lose my benefits before they even end because I fail more than 2 classes?

I'm not aware of any rule where failing causes you to lose your benefits. But you will have to repay the TA for your classes at a minimum before being allowed to use them

You don't lose the benefit but you need a 2.0 to receive them.

Failing classes has ZERO impact on your GI Bill. You can use your GI Bill to retake the classes failed etc. However; the following link may assist with further questions:

https://gibill.custhelp.va.gov