I really like those the Fiesta STs.
My tow vehicle when I was doing lots of track days was Miata. Towed my Street Triple back from Minnesota last summer with my 05 Mini Cooper. Still use it for my trials or dirt bike when I am doing long day trip rides and dont need to pack a lot of gear. Gets more than twice the mpg of my Rover. Just need to do a little experimentation/adjustment of your chocks to get your tongue weight right. Congrats on the trailer, little cars are cool.
Alex started a good list of tires. You are going to get a ton recomendations for tires. Everyone has there idea of what works best. Are you looking for longevity, budget limit, or maximum dirt traction?
My go to dirt tires on the YZ at home are the Maxxis IT (non desert) or the Dunlop MX52 or AT81. INT/Hard tires for most of our conditions here. Just my opinion, others may vary.