This is all very interesting, and it clarifies many things I've been
wondering about aspect for years..

But I've been wondering, with regards to how the {-moH} fits in all
this. Please read the following sentences, and tell me if you would
agree with the way I understand what they actually mean:

DevwI' vIQuchmoHpu'
I have caused the leader to be happy, but that happiness is over

No, it means I caused the leader to be happy, and now my causing that is over. In other words, my action of making the leader happy is complete. Whether the leader is still happy or not is not mentioned.

DevwI' vIQuchchoHmoHpu'
I have caused the leader to be happy, and this state of happiness
continuous. It hasn't ended.

No, it means I caused the leader to start to be happy, and my causing it is completed. Whether the leader is still happy or not is not mentioned.

The difference between these two sentences is very slight: it's the difference between causing something and causing something to start.

And there's something else, I'm wondering too..

SuStel:

jIQuch rIntaH
I set out to be happy and accomplished
being happy, and that happiness is over forever.

I can't understand the "is over forever" part of the translation. Does
the sentence {jIQuch rIntaH} exclude the possibility that the speaker
of the sentence, can become again happy at some other time ?

I revised my analysis after Lieven made a suggestion. It should be interpreted as me setting out to be happy, achieving happiness, and then that particular happiness ends. The rIntaH adds the connotation that the happiness I once had cannot be undone. It doesn't mean there cannot be future happiness, just that that particular happiness is achieved and done. Imagine, for instance, someone going to an amusement park for the express purpose of being happy. They go, they have a great time, they leave. The happiness is over, but it was very satisfying. To lend weight to the statement, the person adds rIntaH to mean that the happiness experienced that day cannot be undone. Whatever happens next, I had fun today.

But it's really not clear whether Klingons would use rIntaH on a verb of quality. I'm just analyzing what it would mean if it were allowed. There's no rule against it, but there's no real indication that it would be used, either.

-- 
SuStel
http://trimboli.name