Much meat in this post, Sarah, way to go!
Regarding the Autonomic responses in Mexico: you can't climb up to ventral vagal when all your surroundings are unsafe! You go between survival shutdown and survival action, and that makes sense if there is no social support in sight! But obviously, now that you have left and are back to some safety, you can climb up to ventral vagal again.
That was a big resolution! Much drama and emotional charge stored in the tissue especially in your left side of the face and forehead (what's your handedness?) is now being released, no wonder it is swollen, because you aren't back to balance yet! I guess while you're fine in Brazil, you still miss your cat which mixes up your regeneration with an unresolved stressor - the separation.
I'd suggest you tap on this issue - the concerns and feelings around your cat, that you lost him out of sight, that you long to feel him close to your skin, whatever "guilt" there might be connected, etc. Tapping can bring out "congested emotions" and it then brings us into a peaceful state that supports autoregulation.