I also recently began teaching 3rd grade after teaching high school for many years.
I have found that Parshios Vayetze - Veyechi as well as the beginning of Sefer Shmos have a lot of Rashis that have vocabulary that is accessible to this age. I try to teach 3-4 pesukim a day so on average I will hit a rashi every 1-2 days. There are basic Rashi vocabulary words and technique that can be highlighted based on the Rashi. For example the word אלא or לפי, questions, answer, pshat, drash, etc.
I would add to the skills you have listed the ability to break up the rashi into phrases. The way the 4th grade teacher does this is initially giving worksheets where she writes how many words are in a phrase and then having the student recopy the rashi one phrase per line on the sheet. As the year progresses, she doesn't tell them how many words are in each phrase.
