Hah, right. I'll gloss over the number of assumptions about me that you make and we'll just address the real crux of the issue.
Biking 15 miles to work is not practical in 100+ degree weather with humidity averaging between 60 and 90 percent. Moving to be within biking distance of work is not practical when jobs change every few years and there are two of us living in the house which is fairly central to both workplaces.
And I wash the interior of my car yearly - your phobia about 'dirty car seats' is fairly silly.
I'm curious. Isn't the breeze you get when biking enough to cool you down? I live in Denmark and we don't often have that kind of weather, but the breeze that you get when riding your bicycle can be really nice in the summer.
I've only experienced Dallas summer heat, but no the breeze doesn't help. I would leave work and it would be ~105 F (40.56 C). I'd get in my car and roll down the windows until the A/C started working. The air that came in while driving would feel like the same temperature as the air in the car, like a hair dryer or something. It was like an omnipresent inescapable oven. Imagining THAT with 80% humidity sounds unbearable.