I have use avocado oil with pretty good success on cast iron. I also have some grape seed oil as well. I have sanded one or two pieces to smooth them some. It does cut down on the time to rebuild a slick coating. Lodge makes a rectangular griddle also that works okay for smash burgers and such. I have one of the large cast skillets. Certainly doesn't fit into the sink very well when clean up time comes. I would think food from cast iron is probably safer than food from whatever wonder coating they have dreamed up for cookware these days.
One could always go the the Himalayan salt blocks for cooking. They look to put a great sear on a steak. Good to here the Pup is doing good.