Thank you for your question regarding Region Transfers. Please check the answers below:
1- You are correct in that houses do not carry over when performing a region transfer so it is important you do away with your houses in whatever manner is more convenient to you before moving servers. There are no reimbursements for lost items due to a server change.
2 + 3- It is recommended you empty your houses before selling them in order to have better visibility of the items you are taking out. The system would normally send these automatically to town storage but if it is full you may lose something in the process.
4- The main post on Paid Region Transfers does not state you won’t be able to transfer while being encumbered so you should be able to unless any specific message comes back when you try it.
I hope this clarifies your questions and see you in Aeternum!