Agreed about showering. I'm lucky to have been born with weird genes, so I sweat very little. For this reason, my advice doesn't tend to be too helpful.
One thing I do is to leave in the morning before the sun has cleared the trees and houses, so it's still relatively cool except on the absolutely hottest days in Wisconsin. And I slow down, and ride with an upright posture, which may help with air flow.
I wear synthetic hiking pants from REI or similar. They have held up quite well to daily bike commuting, about 4 miles each way on relatively flat terrain.
Winter is another matter. ;-)
What's happening to your pants? Maybe baggy shorts over your regular pants would protect them. Lots of people also wear mountain biking garb, which tends to be somewhat less form-fitting. If you're wearing holes in your butt, maybe your saddle is too high.
At least five of my work colleagues have gotten e-bikes.