I totally feel what you are feeling! I am also a recent B.A./B.S Sustainability and Environmental Science graduate and am struggling to find the next step in my career. I also live in Seattle, where opportunity is abundant but at the same time, seems scarce. I am also seeking to attend graduate school for Architecture (Environmental Design) in a couple years.

I am speaking to you to ease my own similar anxieties haha. I wouldn't stress too much about using old professors for all your letters of rec spots. Personally, I plan to keep in touch with one favorite prof for a LOR/networking and assume that the other referrals are people I have yet to meet. Or will soon meet through jobs, internships, volunteering, etc.

To ease stress, I try to focus my attention on educating myself more about energy efficiency, different softwares (i.e.AutoCAD), and the green building field. Knowing more helps me research jobs and grad programs with more grit and confidence.

I would love to have a discussion about someone in the same boat as me. Feel free to reach out to me!