*EDIT* also, say I level up five times, but don't rest, raising Heavy Armor by 10 each time. When I finally do rest, can I only add 5 to my Endurance attribute, or can I ad more? In this case, can I add 50 points?
No, the most you can add is 5. However, if you're able to level up more than once, you can "nap" however many times you're eligible for and level up several times in succession. You need to be careful with that however, or one attribute will be way ahead of the others, causing your character to be weaker that you'd want.
For the training area, it's probably Pyrite's Shrine, which is east and across the river from the Imperial Bridge Inn, just east of the Yellow Road. The worshipers are frozen there, and since they won't die and there's nobody around, you can attack them all you want. There's a caveat though, from the http://www.uesp.net/wiki/Oblivion:Peryite:
If you attack the worshipers excessively, your game may be become unstable due to all the unreported, zero-bounty assaults. This can result in crashes when saving the game, or even when fast-traveling. Legally resolving a crime clears out all the "unreported" crimes which are overloading the engine. Simply commit a crime that is reported (steal a worthless item and get caught, or punch a guard) and then pay the fine to fix the issue. It is probably safest to do this periodically instead of waiting for your game to become unstable, because once your game starts to crash it may be too late to recover.
» Fri May 27, 2011 10:25 am 
