Your college GPA is great and above for what Michigan is looking for in a transfer student. https://admissions.umich.edu/apply/transfer-students
It is still competitive but you seem to be on the right track. I wouldn’t explain your grades. They are fine. The Sat is on the low side but if you are coming in as a junior standing I think they dismiss your high school record. You’ve done great at state!
Your essay should be unique, interesting and personal. Your work at the child development lab sounds interesting to me. I would want to know more about that plus your volunteering VS work study/job. That shows me you might have a true interest in that area /field.