Totally agree with this, and that was with the stock 700x25 tires. I imagine one with something wider must be amazing.

I would be on the lookout for a different bike. Some department store bikes are worth tuning up and riding, but a low-end Free Spirit generally isn't worth it. They tend to have incredibly heavy frames and wheels, to the point where I would not be surprised if the rear triangle was made of solid bars instead of tubes. They also have plastic shifters that must be replaced, which might add a considerable cost if you have a bike shop do it.

Mountain bikes can be comfortable for road use if you switch out the tires, bars, and maybe stem. I don't know how well this applies to newer ones, but older ones might just be the best base for a city bike out there, and converting them to touring bikes isn't unheard of. Out of all the bikes I've owned, I've put the most miles on my '95 GT Pantera MTB with the tires and handlebars switched out, and have been fairly comfortable, though a different stem and saddle might have made it a bit better.