Given only the information you stated, your licensing number assumptions are correct assuming that the secondary controller will not host any devices of it's own. I do recommend having one license on that controller though, just so you can bring up a local phone if necessary for testing purposes.
AMC does not know, or need to know, that the second controller is resilient, this is handled but he controllers themselves with clustering and SDS.
A group ARID in this case is optional, you are not using UCC licenses, so it it is not required, but if you are going to make the primary 3300 the DLM, you would use one.
If you have issues or questions about licensing requirements and configuration, you can always contact Sales Engineering, they can usually answer most questions pretty quickly. If you have questions about actually building the license records, AMC support can usually assist as well.
