they will work fine. 245 is ranged for 8-9.5. 8.5 is actually the recomened width.
255-265 would look a little more squared off.
275 is actually on the wide side for a 9" rim even though tons of people run it.
no whether that will alow you to curb the rim or not I don't know. there was a mix up when I bought these wheels and tires I got 18x9 up front instead of 18x8 so I have 245 on 9" right now. bfg kdw-2 and the tire hits the crub first. I tested it out to make sure I did not have to give the wife a lecture about curbing the rims.
I'm just afraid to run a 285 on a 9" rim if its unsafe or too wide.
I agree with you on the 245's on a 18x9" wheel. Mine are fine and seem to do the job. I don't believe its completely necessary to upgrade to a 255 or 265 up front.