关于 "permanent" in employment verification letter

I-485 application:
Here is an example from my lawyer:

Dr. xxx is currently working for us as a _____________. His employment with us began in _______________, and is expected to continue on a full-time permanent basis. For Dr. xxx’s skills and services, he is remunerated at an annual salary of $_______________.

我的问题是：
1. 老公所在公司拒绝 “permanent" 一词，理由是所有的工作都是"at will". 如果去掉"permanent"一词，行吗？ 我们律师说不行。类别： NIW.

2. 我是F-1 （research assistant), 是否也需要 employment verification letter？一样的版本吗？

谢谢