1. Agreed.
2. The rules say otherwise. They say 'a portion' of the deck should be removed from the deck top and put on bottom. 1 card is a portion. 59 cards are a portion. It doesn't say 'a portion somewhere between 2 and 58 cards but not including the numbers 7 and 13'.
3. Pile shuffling is a great way to make sure your cards aren't sticking together, creating clumps. They're also a great way to make sure you didn't mix up your BTS with your last opponent, since you'll be able to tell if you've got an uneven amount of cards. As long as it's done in a reasonable amount of time, there's nothing wrong with pile shuffling, and it's actually a really good thing to do. Not sure what you mean by 'crazy off the wall cuts', but I'm pretty sure my #2 covers it.
4. Absolutely have fun.
5. A lot of times, by the time you 'figure out' someone's a cheater, they've squished you. There's basically no way you're going to be able to RELIABLY sniff out cheaters and cut/shuffle only their decks. Treat every opponent the same, cut all the time. Someone acts shifty (Shiftry?) sure you can/should shuffle their deck. But honestly, don't think you'll be able to tell a cheater before they've already cheated enough to win Even then, it's questionable. We've all hit on the hax of the game at some point. Amazing hands happen to everyone. They ALWAYS happen to cheaters. If you only play once, how do you tell the difference?
6. Why not? Equality for all. Really, I covered this in #5, but to reiterate, you don't know who is a cheater. Even a friend might give in to temptation and stack, especially if they happen to see an opportunity and they want to win. Shuffling decks is a good equalizer. Plus, it keeps whoever you're playing on their toes. I can't count the number of times I've shuffled someone's deck and they respond "Can you do that???" It's good for everyone to know their options.
7. Absolutely. But should they have to? Judges can be busy people. This is particularly true at BRs, where often there's only one judge over all the divisions. Calling a judge over to shuffle a deck you could just as well have shuffled yourself isn't necessarily a good use of resources. I'm sure most judges would be more than happy to shuffle a deck, but most would prefer it to be a Junior who is having trouble versus a Master with a superstition.
8. There is no 'superstition of losing'. Losing is an option every game. It happens. Losing in an honest game, even if it's a donk, is better than losing a dishonest game to a cheater. Especially true if you could have prevented it yourself just by shuffling or cutting. It's not superstitious to think you might lose, and it's not superstitious to try to keep the game honest.
TL;DR: Shuffle, cut, try to keep things light. It's not really a part of the game you're supposed to dwell on.