That is a lot of questions, and you probably should consult your Aruba partner or local Aruba SE to get the better answers for your specific situation.
A1: there is no concept of WAN interface on standalone controllers. You can put any interface in any VLAN and do routing and/or NAT on the VLAN interface to achieve 'WAN interface' functionality.
A2: You can do this with policy based routing. With Aruba SD-Branch, it is much easier to set such things up.
A3: What is likely is that you may have limited the allowed channels that ARM can pick from to a set that does not include the channels that are allowed for outdoor operations. Or if you have an AP with external antennas and not configured the antenna parameters. Quickest is to consult an Aruba partner or Aruba Support to find out what is happening.
A4: You probably have a routing issue (if NAT is done outside your controller) or not configured NAT on the outgoing traffic.
A5: Yes, if you enabled telnet in the AP System profile, but there is not so much to see/do on a campus AP as it just tunnels to the controller.
A6: This is covered in training and the product documentation. That is not brief but I'd advise you to either have it set up for you by an experienced engineer or invest in training and learning how the system works which may not be a brief exercise. Without good understanding there is a significant risk of misconfiguration which may lead to insecure or poor performing implementations.