Well vulching is a tricky one, I have at times indulged, and at other times refrained.
If we are 2 minutes or less from a solid field capture, you bet I'll kill them on the runway.
The field is capped, town is down or almost down, troops are on the way, its the smart thing to do.
To kill someone on the runway just for the easy kill, now thats a harder nut to crack.
Again the answer is going to depend on the situation. But smart players know not to take off from fields that have enemy planes circling overhead. Dieing more than once like that reverses the karma, if your silly enough to do it twice in a row, well you have it coming.
On the HO, first lets clarify what is a true HO, and whats a forward quarter shot in a manuver fight. Which has a stigma attached to it and why, and which doesn't.
The true HO is one where both planes are nose to nose at a distance, and both drive in going for the shot.
A lot of new people only learn this tactic, and how to continue to run, not turn and fight. Hence the stigma attached.
Its a low skill no ACM required tactic, and if its all you can do, it sucks.
However, say you and I meet on opposite sides, see each other and 5k out, and turn at each other.
I duck under you as I come into range, thus dodging any possible HO shot. We both immelman Up & over and meet again at the top. Granted we are both nose to nose, but thats NOT a HO, its a hot merge or a forward quarter shot in a turn fight.
We are BOTH doing ACM, trying to get behind the other guy, and there should be NO stigma attached. First guy to get around gets an advantage on the shot and thats as it should be.
Now you'll hear a lot of guys CALL that situation a HO, mostly because they just died. A good pilot seeing this situation coming as he comes around will kick some rudder, change his pitch input, to spoil the other guys shot. Because its NOT a HO and go situation, there is and should be no stigma attached. Both planes have an equal chance, both pilots have options.
This tends to be a hotly debated subject, and a sensitive one for me.
Partly because I feel that it is a lack of education on the Trainers Corp that results in this debate.
If we had done a better job earlier on of defining what is a HO and what isn't, what is accepted, and what shouldn't be.
Frankly we wouldn't be in this mess. But for most of you thats water under the bridge.
So at what point do you seperate a "good" hot merge from the "Bad" HO. Myself and some trainers like to put that boundry out about the 3k point. If you extend beyond 2k just for another chance to HO, the stigma should reattach itself to your actions. If you are flying in a pony, extending to about 2k is required before you can reverse in order to get your guns on him and keep him from trying to shoot you without the possibility of you shooting back.
However some pilots are firmly convinced that if both pilots have their guns on the other guy its a HO. And that if they die to that move they have a right to complain loudly on 200 or private. Again mostly because of THEIR lack of skill, ability, maturity, or ego. But then they don't want to hear that now do they.

In FSO, there are no rules other than the clearly stated ones. 1 life for all, follow orders, stick with your squad, do your best.
If there is a problem, say nothing, let the CM's deal with it. Or bring it to Daddog, teerex's or my attention.
Malap I think your solidly on the right path.
However there are a few notable exceptions to remember.
Anytime I have 2 or more enemys engaging me, with no friendly inside of 3k to help, the gloves come off. Your outnumbered, you take ANY shot you can get, at ANY time and don't sweat it.
Any time I see 2 friendlys on a enemy I prefer to stay clear. They don't need the help, and he has it bad enough with 2 on 1. He sure doesn't need a third con dropping in on his 6 to worry about. This is where class shows, and you start making your reputation for good or ill. Thats not to say I will never do this, I stole a nice kill from daddog and baumer last week.
But that was more about stealing a kill from them than any desire to gang bang an enemy.
A 1 on 1, where its unsure who's winning I'll ASK the guy, "need help?" "You ok?" or something similar.
If he wants help my preferred tactic is to buzz the con once, but not fire. Get him to break, equalize the fight, then zoom back up out of it.
If he is behind the enemy, I'll shadow along, stay high, and watch for incoming planes.
Keep his 6 clear and warn him if any other enemys show up.
If its a furball, its first come first served, teamwork tactics WILL earn you friends.
Apologizing for stealing a kill from someone if you really didn't mean to, will also help.
I keep a mental list in my head of people that have repeatedly helped me out, or shown class.
Guys that consistently clear your 6 or give you "good" check 6's. Squadrons that have shown up JUST at the right time to tip the contest in our favor. Guys that don't try to jump in on an enemy that you've fought with from 8k to the deck to steal your kill. In short the guys that I like to have in the sky around me. Class acts, solid folks.
I also keep a list of those who have recently done me dirt.
Kill stealing, diving in front of my guns causing me to killshooter myself, shooting at a enemy after I've shot a wing or tail off.
(this is part of the reason I like to "announce" kills on range, let people know he's down or dieing)
Guys who are known to prefer flying in a 3 + swarm or horde. Or guys who are just plain nasty on voice, etc
I see one of these guys show up and I'm looking for another spot on the map to fly.
Everyone over time develops his own set of ethics, and over time this significantly impacts your reputation.
By the same token, worry not too much about what others think.
And if you just killed them, ignore anything they have to say other than a <S>.
Its really not worth listening to.
I do like to <S> anyone I've killed. It takes some of the sting of dieing out for them, and costs me nothing.
If they were truly a worthy adversary, they will get the <S> and some complements. Awesome fight, great moves, good shot, etc.
I always try to be gracious in victory, and humble in defeat. Granted thats an ideal I shoot for not necessarily who I am.
But that is the goal is it not?