1) Mail drops are not as popular as they used to be, and resupply on-the-fly seems to be the most popular method right now.
The mail drop method allows you a greater amount of control over your diet, so people who have dietary restrictions still tend to prefer it. Hikers who are content to eat whatever comes to hand and like the freedom to follow food whims tend to prefer the on-the-fly method.
The on-the-fly method does sidestep the problem of appetite fatigue - where you planned to rotate among a set number of premade menus (say, 8 different dinners), and then discover two months into your hike that you can't stand the sight of two or three of them. But you are still scheduled to eat those meals over and over again!
So, it kind of depends on your style, and how well you think it will extend to a five month hike.
2) Try asking this question on the email listserv run by the PCTA. You can sign up for it at the pcta.org website.
3) Snow and ice vary from year to year. The best answer to this question will be available in late March.
4) Bears. Wherever bear canisters are required, you must
use a bear canister.Beyond that fact, there is a whole lot of bear lore around. Some of it is even true.
In my experience, bears are almost never a threat to anything but your food. If you encounter a bear, the standard advice is not to run, but to move away slowly and not approach it any closer. Chances are very high the bear will skeedaddle in a hurry once it is aware of you.
5) If you've never carried weapons, then a weapon is not likely to do you any good anyway. People who suggest this are almost never hikers themselves, but well-meaning non-hikers.
The good news is that crime rate on the PCT trail
is exceedingly low, meaning almost non-existant. Criminals are not often willing to hike into the middle of nowhere on the off chance that they may find a victim. This may not always apply with equal force to places, like campgrounds, that are accessible by car, but even then, it is not exactly a hotbed of crime there either.
If you haven't yet discovered it, may I suggest perusing:http://www.pctmap.net
There you'll find a treasure trove of printable PDF maps in 8.5" x 11" format for the PCT. They are free for downloading.