Is it normal i don't know how people make moral distinctions?

This is fundementally about the definition of words, dude. Murder is killing someone out right without it being in a war or something. Where as execution is normally due to a crime being commited and someone being put to death as a result of that. It's kind of like not seeing the distinction between beef and pork. They're both meats, how can people tell the difference? From simple qualifying areas that group one thing seperatly from another.

Many people want to see the world in stark black and white terms because it makes life easier. This is the appeal of religions: you're given a set of rules where some things are always wrong and other things are always good, and all you have to do in order to live correctly is comply with the rule book. That relieves you of the responsibility of having to think too much about your actions and gives you a clear, simple, easily understood framework for you to judge the actions of others.

The reality is that moral judgements are always subjective, and a society's rules of morality are a collective decision of that particular society at a particular point in time.

Killing other people is a pretty universal no-no. That makes sense, since no society will function well or survive long if everyone is allowed to murder anyone they choose without suffering any consequences. But virtually every society through history has deemed it morally correct to kill outsiders who are deemed to present a threat to the society's established order. Some societies choose to consider it morally correct if the ruling structure goes through some process which apparently proves a member of the society has done something against the common good, whether that be questioning the validity of the society's rulers, challenging its established religion or killing another member of the society without any justification. Some societies choose to consider it just as morally indefensible for the state to kill someone as it is for a private individual to kill a person.

You're far from the first person to ask the questions you pose in your OP. Western philosophers started thinking about morality at the start of The Enlightenment in the 18th century when people began to seriously question the validity and value of a book written in the Iron Age. This is a subject you could spend your entire life pondering if you chose to do so. But it seems to me that the fundamental point is that morality is a human construct, and the onus is on each of us to determine a few facts that we personally find indisputable, and to figure out the rest of our personal moral universe from there.

The last half of your statement shows you to be very capable of making moral distinctions. Yours are getting a bit all encompassing for my tastes though.

Morals are kind of subjective.

You just have to use logic. The level of necessity is often an important factor, and how much damage/suffering something causes (that makes things immoral). As well as what benefits you get out of it (especially when many benefit from it), having a great benefit output makes something more moral. Its not an absolute

The government's job is to keep society as moral as possible, and it can do what it needs in order to obtain that goal, as long as it does not cause more evil than it prevents.

The purpose of marriage is to make sex moral. Outside of marriage, sex is immoral, but within marriage, sex is moral; that's just the nature of marriage.

Yes, killing in self-defense is still killing. I would suggest that it should still be confessed. I would doubt the mortality of the sin, though. It would likely be merely venial.

We are told time and again that all of the animals and plants on Earth are intended for our consumption. Remember, plants are alive, too. Everything alive must eat other things that are alive, or else they will not be able to live.