Remaining Language API questions

Hello, over the past week or two I've posted some Language API
questions. Some of you from JB and from the community have helped me out
but there are a few questions that I'd like very much answers to, which
have not been answered. I hope this re-post will make the questions
visible again so someone can answer.

1. "Language API: how to embed languages within each other?"

I want to embed HTML, CSS, and Java into a custom XML language. I also
want to embed Java into another custom language. Is this possible at all?

2. "Re: Language API: custom XML file formats"

Dmitry Jemerov answered part of my question, but it still remains: is
there a way to define custom XML formats with custom completion of tag
names, attributes, and contents?

3. "Find Usages only partly works"

Eugene, Dmitry, and Maxim Mossienko helped me out with this, and the
situation has improved for it, but find usages and refactor->rename
still doesn't fully work for my language. When I refactor->rename, the
item is renamed, but references are not changed, etc. Will someone go
over the steps required to support these features, including who should
implement what, and what should return what?

These are all of my questions for now, I hope someone can help me with
these problems.