1.) I never felt the need to redose because I would always just take the pills I had all at once (50-120mg's hydro). i always got the best high this way, never had to worry about "re-dosing" to "boost" the effects or anything. I dont think its necessary.
2.) No one can tell you how much you should take as your "max" dose. Only you know your tolerance and only you can make that judgement call. My best guess is that if you only use 25-35 mg's to get a "nice high" than you shouldnt ever go over 50mg's. Thats just my opinion, and im not a doctor, so dont take my word for it.
3.) Definitely on an empty stomache. It kicks in MUCH faster(especially if you crushed the pills or broke them in half). If what your looking for is that blissfull euphoric high that wraps you in a warm blanket of happiness than I would definitely do it on an empty stomache. this allows more of the drug to hit your brain alot faster....allthough, it probably also leaves your sytem faster(but not too much faster), so if your looking for a prolonged high thats not quite as good as the "empty-stomache" one, then maybe taking the pills after you eat is a good idea. It all depends on your preferance.
*I never got too nautious from opiates but when I did I actually enjoyed it because it meant I was blissfully high and the euphoria was much stronger than the nausia. but whenever I did get it, i would just lie down and it woudl go away. If your in a situation where your going to have to be up and walking around, than you might wanna take the pills with a little food to prevent the nausia.....also, taking it with some pepto couldnt hurt.