"-ise" as opposed to "-ize" is a difference between British English and American English. I guess "travelling" as opposed to "traveling" must be too because all of my spell checkers and stuff insist on the double l rather than the single as you said.
I don't know whether this is a UK/US difference, but "practise" is the verbal form of "practice", which is a noun. Perhaps they don't make the distinction in America, I don't know.
As for the awkward sounding sentences, I'll look over them. A couple I'm sure are correct, but the fact that you've pointed them out at all makes me think that I might be better off modifying them slightly anyway to make them clearer. I have a particular problem with sentences that go on too long and get a bit too wordy, so thanks for pointing them out, I'll edit them now.
Anyway, thanks for reading and glad you enjoyed. And, yes, I always think that a Pokemon's personality should reflect its trainer's somewhat - a bit like Will and his Golduck, if you remember that from Chapter 2.