I disagree completely. You took a couple of rare exceptions and tried to prove a rule that does not exist. Out of the few examples you gave, only one qualifies as him loosing temper to any reasonable degree, and that is “Tear the ship apart!”. The original “Bring my shuttle!” is more of an annoyance and does not really qualify as loosing temper (anyway I prefer SE version). But these two rare examples are eclipsed by the overwhelmingly clam portrayal of Vader for the vast majority of OT.

There are tons of scenes that strongly indicate his clam nature and extreme composure:

“I find your lack of faith disturbing.” (Extremely calm and witty response to a very professional provocation from Motti. One of the best examples.)
“I told you she would never consciously betray the rebellion.” (Even Tarkin gets upset by this point but Vader remains calm.)
He remains surprisingly calm even after one of his wingman rams his TIE fighter at the end of ANH. Probably the most irritating moment for him in ANH and yet he does not loose his temper in the slightest.
“You have failed me for the last time Admiral.” (This line is said in a very clam and cold manner. No sign of loosing his temper, even though Ozzel screwed up big time. The tonal stress on “last” is just a natural speech pattern since the word “last” should be stressed.)
“Apology accepted, Captain Needa.” (Extremely calm and witty line, even though Needa screwed up big time. One of the best examples.)
“Perhaps you are being treated unfairly?” (Calm and witty response to Lando irritating him.)
“You are beaten. It is useless to resist.” (Even though Luke cuts his arm, he is completely clam just moments later.)
He does not kill Piett at the end of ESB and just calmly looks around the space and walks away. His body gestures are evidently super clam in this scene, which is even a bit surprising.
Pretty much the whole ROTJ is one big example (especially scenes with Luke).

Loosing temper and lack of composure are signs of weak-minded losers who can easily be controlled by the cues from the outside (words, situations, etc.). Sorry but that is not OT Vader, no matter how much you want to retcon the horrible portrayal of PT Anakin.