I can't even remember the last time I saw a gravel road --- oh wait I just remembered. The last time I saw a gravel road was 24 years ago way out in the boondocks of eastern Oklahoma.
that's a pretty good hit on the windshield. I used the RainX windshield repair kit on a chip half that size and it worked great! Since you have the cracking already its probably too far gone but maybe worth a try for under $20
Interesting...I had the same issue happen to an 1995 oldsmobile I had. I wasn't sure where it was coming from so I just drilled a small drain hole through my floor pan LOL