求教Xiaobaitu, I-140 was denied!

my I-140 (via EB-1b in NSC) was denied. the reason is that I did not submit the official job letter, but my lawyer said this is just an excuse. Because I cannot prove that my position is permenant(I am a research-track rather than tenure-track faculty), he thinks it is a waste time to appeal and suggest me refile under a different category.

Now my only choice is LC, but no one in my department (even the administrator) has such an expereince. So, my question is: 1) is there any easy way to do LC in university setting? especially, is there any way to avoid advertisement (I know there will be tons of interviewers if the position is advertised)?

Many thanks