I just want to ask, is it the norm in the US for ATC to read out :
Cactus Fiftheen Fourthy Nine
Instead of:
Cactus One Five Four Niner
Yes, it is. On the initial call to ATC, the aircraft gives the full callsign, as you do. ATC will also give the full callsign if they make the first call to the aircraft. ATC has the latitude to shorten call signs depending upon workload and who else is on the frequency.
Why exactly, I don't know, but it does seem to work in the U.S. For a non-native speaker, it might be harder to do, but ATC is usually reasonably sensitive to that.
American pilots can (and I am one) be sloppy with R/T, so you need to listen not only for what you expect to hear, but variations upon it as well. Unfortunate, but true.
Dream Buster-
I'm not sure I'd call the
Shiga a ditching. I'd call it a lucky instance of CFIT. Curious how I'd never even heard of it until today. I have, however, been using the Asoh defense for years... I just didn't know it was called that.

Now, PanAm 943...
that's a ditching.