How do I grade the evaluations at Mid-term?

There are a couple of ways to do this.  You will need to use your own judgement here, but here is one thought.

Create two grade books in eee, one indicating quantity and the other quality.  In the the quantity grade book, simply check that students are keeping up with their sources and evaluations each week, noting the number per week.  Do not read the evaluations every week -- just count them up as aligns with your source and evaluation requirements for the quarter.  Then two or three times during the quarter, read and assess the sources and evaluations in line with the rubric and with what you have emphasized to your students.  I recommend doing the first one at the two week mark, but some people do it when each paper is turned in, or once at week 5 and once at week 10.  You have to plan ahead and look for those little gaps where you see you will not be reading drafts or grading papers.