4.5.1 - I don't understand the purpose of the new path option.
The path option was added in the earlier v3 preview release. It's really the same as the operand in v2. The path option will be removed to avoid confusion.
2
Clarification
4.5.3 - I assume you're going to support both the old directory and the new directory, for compatibility with existing v2 domains.
Yes
3
Clarification
4.5.3 - I assume you're going to support both the old domain.xml element and the new element, for compatibility with existing v2 domains.