Definitely much safer running 275/35 and 305/35. It's what I'm running on 20x10/11. To be honest the 40 series on the 275 up front is too tall for my liking.
I guess it depends on the salesman. I also bought mine at Galpin and everything went fairly smooth. I almost purchased from Autonation Torrance. They weren't bad either. I had the worst experience at South Bay. They actually told me to go to Galpin because I wanted a PP/Recaro S550.
Yeah, seems like it's more for watering plants. I use a 1750 PSI 1.3 GPM pressure washer for my foam cannon and it works well. But it doesn't work so well for heavy duty stuff.