Yes, must replace tires. 12 year old rubber. Only 21000 miles but tires are well beyond their lifespan. Car and tires real shiny. Easy to forget that old rubber. New tires in the next few weeks.I'd replace your original tires first, not that it has anything to do with your ride height.
I typically set my height off the lower control arm mounts. They tend to be in similar locations relative to the rest of the chassis on all kappas regardless of if it's a solstice or sky, or how well body panels are aligned.