1) If you do it correctly, you don't have nothing to be afraid of. But imo it's always better modifying an existing one rather than creating one from 0.
2) Yep, Pkhex do that. If it's a tradeable you can just put the file in your game and use it normally (If it's legal, of course).
3) Yep, it's possible.
4) Yep, if they are tradeable Pokémon, you can get them by just putting the pk files.
5) Pkhex simulates the Transfer process, you can always check if the data is correct after just dragging your files.
6) Yep, you can get them via VC so there are some moves that are legal if the Pokémon has come from those games.
7) From Gen VI onwards, It doesnt matter the country where you are, you can choose any language you want, so a Pokémon can be from Japan and have it's name in English. You can do that to the Pokémon, but the Sub region and region should match.
8) I think it refers to the meeting of the OT and the Pokémon but Transferred Pokémon via Pokébank from older generations have their "Met Date" modified when transferred.
9) Pkhex keeps updating it's legality date. It has a legality check that is always helpful to get a legal Pokémon and tells you what is wrong if its marked as illegal.