Old kettle, bean pot, looks to be a Number 8 from your measurement description. Not a spider in my opinion. One of the "feet" looks like it is worn or broken. I have restored some rough pots to over the fire use. Watch out for those tiny pin holes, following the brushing and steel wool bath. A soapy steel wool pad will work. Turn it upside down and watch for tiny bubbles. Like checking a tire for a leak.Make sure all rust flecks are gone, scraping with a wood spoon. It's a big gamble to clean up an rusty old pot like yours, but it can be done.
I use a open fire grill grate to slowly heat the cleaned brushed kettle. Heat and coat with multiple layers of lard, focusing on the inside cooking surface. Once seasoned bring the kettle to a rip roaring boil with water to make sure no small flecks of rust pop out.
If small a small hole emerges, well, you tried. Two options, make it a planter or drill holes in the bottom and make a grate. I have sold many restoration failures as repurposed grills.