Is there a reason why you aren’t just using the native Bluetooth output of Reach RS+? It doesn’t seem like a RS232 → Bluetooth adapter is necessary unless distance is an issue.
edit: After a closer look at the picture, I see it is a long-range bluetooth adapter. And I think I found the problem:
So it is an older unit, and in the text there it says that it needs the legacy GP style NMEA messages (GPS constellation only), where Reach outputs GN style messages (multiple satellite constellations).
An alternative wired solution would be to get an adapter for the iPad that gets you a USB port, then a USB-serial adapter. You could plug the RS cable into that.
Or you could try using plugging Reach directly into the iPad USB adapter.
Another possible solution is that you could put a single-board computer in line to read the GN messages and then output ‘fake’ the GP messages to satisfy the AMAN unit.