Early welcome to you!
Let me try to answer your questions:
1) Yes your items/zeny will likely be limited. I think I saw screenshots of your attendance rewards before. We don't have items like Angel's Kiss, so mostly likely those will be deleted if you come over. With most mergers, your items are also (sadly) bound to your characters.
2) Regarding bugs, sadly we have the same developer/bug fixer: Gravity. So whatever bugs you have, we probably have. If you don't have a fix for it, we don't have a fix for it either. We're all suffering the wait together. Warpportal staff/GMs/CM do not directly fix the bugs, but they are here as support until the bugs can be fixed.
3) Our Colosseum times are 1PM, 6PM, and 1AM Pacific Standard Time. Our WOE is 5PM Wednesday and Saturday.
Personally I have no experience with Thai players, but in general, as long as you are a good person, you'll be welcomed well. If you have bad manners, you will be treated with bad manners.
4) EDIT: I'm not sure about Facebook IDs, but most likely they'll be able to make Warpportal accounts in order to access our servers and you will bind your character data to your new ID.
Hope that helps!