You have some points of disagreement with the way the actors and director portrayed the weapons scenes, which may be quite accurate objections. However, your words "totally" and "unwatchable" are extreme and absolute. For those of us with less experience in weaponry, there was still much to learn from the film.
I was struck by the two scenes of the children handling weapons, the woman and child approaching the squad with a weapon hidden in her hijab, the scenes inside the home where a meal was served and then a weapons cache was discovered, the outdoor scenes showing both the countryside and the towns with satellite dishes all over the primitive houses, the uniforms and equipment in general, the scenes in hospital with the wounded, his interaction with the wounded, and many other things, including the news footage of Chris Kyle's actual funeral procession and funeral in a stadium in Texas. My experiences with combat wounded as a volunteer at Walter Reed were well represented in the film.
It's good to take movies with a grain of salt, or even a bag of salt, but overall, the film was not so distorted as to mis-portray the main gist of the story.
If Chris Kyle was on the phone with his wife during a firefight, he was derelict in his duties. Leaders lead, they don't distract themselves from the mission and leading those around them. In combat, distraction is death.
The movie had some small OK moments but in the main, it was amateurish and unrealistic. Note to people who want to make war movies: incoming fire makes a ton of racket and when somebody's hit, it makes a loud bang like breaking board. You almost never see that many enemy out in open. They're not that stupid.