I have an iAV 5 dock I can not get apart

This is typically a damaged 30 pin interface. It’s all too common on all of the docks that use this interface, just because of how fragile the connector is. Lighting docks are a lot better and fewer tend to be broken, so Apple learned their lesson when they changed the connector. My iA5 isn’t broken but that’s because the previous owner didn’t get around to it and I’m careful with it because I know about this problem all too well from seeing it multiple times.

If you see obvious dock interface damage, consider the 30-pin interface “dead” and use a 3.5mm aux cable or Bluetooth receiver - it’s usually not worth replacing the bad connector. I use a Bluetooth receiver on my older Pioneer receiver that rejects modern devices and it’s a viable option - just charge the battery once in a while and it’ll be okay.