Asking for letters of recommendation? Who is appropriate and when should I ask?

Hi! I am currently in my second year of teaching and I have been with the same school both years. When I came out of college, getting letters were pretty straightforward--I got letters from my cooperating teacher, my university student teaching supervisor, and some professors I worked with a lot.

This year I'm looking for new jobs, largely because I work about an hour away from home and I'd really like to relocate closer. I am also not particularly happy for various reasons that are neither here nor there. But now getting letters isn't as straightforward, so I guess I have some etiquette questions.

So my questions are these:

1. Is it inappropriate to get a letter from a co-worker? Last year I co-taught with a very experienced and well-respected teacher in my area and I feel that her recommendation would be helpful to me, but I'm not sure if I would get side-eye for having a letter from another teacher, like it might look like I just asked my teaching friends for recommendations.

2. Is it inappropriate to ask my principal for a letter? I know she is happy with my performance and I know she does not want me to leave the school, but I have also expressed to her the possibility due to distance so it wouldn't be blindsiding her.

3. If no to these, who the heck can I get recommendations from?

4. I should probably drop my student teaching letters of recommendation, right? Or are they cool to still use in addition to updated ones?