Most of us have been there and done that, and had difficult learning experiences. I've had chickens a long time, and can guarantee that I've made way more mistakes than you have!
We learn, and move forward. Predators and biosecurity are the biggest issues, and it does take disasters to inspire that Ft. Knox coop build! Then, it's keeping it in good shape, and enlarging it to house more chickens...
Electric fencing is a great help managing dogs and other ground predators.
Chicken Little needs friends! I just got more chicks from Cackle (chicken math run wild!) and recommend them, and Murray McMurray, depending on where you live.
Mary