For example wrote:

Well it is even more logical than that. Two long is morse M which has the
meaning 'my vessel is stoppped and making no way through the water'

long short short is morse D which has the meaning 'my vessel is restricted
in its ability to manoeuvre ....'.

Not quite, D actually means "I am manoeuvring with difficulty" which
is not exactly the same thing. But similar, I'll grant you.

But the single long blast, T, means "I am engaged in pair trawling".

I think that knocks your theory on its head.