Numbness is not normal. I'm about your size and I can ride 50-60 miles without any numbness. Sounds like you're having issues with your fit, or maybe issues with fitness. Find a bike shop you trust and get them to help you with fit. Taking random advice off the Internet probably won't help! Everybody is different and what works for me may or may not work for you...
Realize that you may need to buy a different saddle before your butt is completely comfortable. I rode for years and tried a bunch of different saddles before I found the one that I use now (Selle SMP Extra, $110 @ Performance Bike). It's great! All-day comfort and no need for that disgusting chamois creme, though I do wear decent bike shorts (Pearl Izumi Slice Ultrasensor).
Finally, you are going to have to learn to vary your had position. I ride on the hoods probably 80% of the time, but the other 20% of the time I'm varying my hand position. You don't have to use the alternate positions for hours at a time, but a few minutes here and there will give your hands a bit of a rest.