Congrats!
I had a cat who was pretty old who had kidney failure. Wasn't sure I could do the subdermal injections he needed to buy him an extra while, but not only was it easy, it was like he knew what was happening (he never ran). He was like that. As long as I didn't put him in a pet carrier, he would even sit very calmly in the car on the way to the vet. Only option they gave him was adopting a second cat and doing a kidney transplant for money I wasn't anywhere near back then.
For others re: vet bills - vets are expected to specialize in almost every field at once for all sorts of very different animals, and becoming one is very expensive. Those bills aren't buying the practitioner as much as you think.
OP: one thing I don't understand... you said you had FI plan of 6-7 years and started almost a year ago, and did very well, and had pet insurance. Were you expecting to spend an enormous amount, or is your pet insurance for a very small amount...? The reason I ask is that if the pet insurance is capped at $1000 or a few grand, you may want to see where premiums get outrun by stock returns and just invest the money (and have more to spend on the animals or anything else).