My suggestion would be for you is to have separate Domains for both Prod and Dev environments even though it is bit of extra work in setting up Domains initially, but it will avoid SPOF (single point of failure) situation in case there are any issues with the server in future. Also it is easier to rollout fixes and patches by testing them in lower environments prior to deploying them into production.
For your other questions, yes you can have Repository and Integration Services on the same machine where the Domain is running as long as there are no resource constraints on the server having the services running in parallel. Initially you can start with repository and integration services to start with and then later add other services based on the requirement and your current licensing structure.
I am not clear on your 4th question. Please explain clearly.