No, and Spinoza is very good on this, arguing that if we feel remorse when we do something wrong, we are adding one unhappiness to another, and instead of working out how to avoid doing the wrong thing, we often rather enjoy being miserable thinking of it. We ought to be active and improve our moral standing, but we often wallow in misery which makes us passive and fixed in a certain character. That said, we could use regret in more positive ways, to move us onto more productive ways of acting and moral improvement. In Spinoza's language, for this to work we really need to orient ourselves towards the future rather than the past when reflecting on our behavior and this is very difficult to do. Quite rightly though he did not conclude that we should not set out to attempt it.

There are, and meaning is one of them.

Nothing at all, they can be hilarious. Just like racist jokes, jokes which poke fun at disabled people, women and religion. The point of jokes is to transcend boundaries of good sense and social propriety. It is alright to object to them if they are objectionable, but that does not mean they fail to be funny. In fact, I suspect that a joke which is not objectionable would not be very funny, unlikely to result in a guffaw.

I think this is a psychological question and no doubt there is research on it, and I imagine it is culturally dependent, since in different cultures colors often have different meanings. When I read your question I could not help thinking though how good it is that we make these sorts of associations, however we make them, since they considerably enrich our vocabulary and the sense that we can make sense of the world. It is also worth noting how potent such associations can be in a negative sense, where we have a favorable attitude to certain colors and perhaps to people we see as having them, and the reverse.

They are, but some are true and others are not, hence the significance of the distinction. It is an important distinction, and the liberty of many people has been curtailed by courts believing that some events actually happened in the past rather than merely imagined. In fact, the legal issue often is whether something actually happened or did the witnesses merely think it happened, and as you say the actual experience in both cases is identical. Our experiences do not come with little flags which wave around and tell us they actually happened, so we are often dubious about the reality of some remembered or imagined event.

I don't think it was the Stoics, and this sort of compartmentalization would be disapproved of by most philosophers, as far as I can see. It is the sort of thing we tend to condemn, like people doing something of which they should be thoroughly ashamed at work and then coming home and ignoring it or pretending it never happened. Philosophers tend to suggest that people need to consider their lives as a whole, considering the effect on their moral character of both their work and leisure activities.

I don't know why you assume that either of these false beliefs is irrational. They are certainly not true but they could be and no doubt there is some argument and theory of which they could be a part and play a role. They are not arguments which philosophy can address directly, since they are biological or economic, although philosophers could address what sorts of evidence might prove or disprove them. A good way of starting is not to assume that philosophy can help us to attain a more rational, equitable, tolerant, and compassionate culture. It can help us provide some explanations of different conceptions of such cultures, but you seem to assume that it is obvious what such a culture would be, and what values it must hold. That is very far from anything that most philosophers set out to do, fortunately.

A good way of starting to get out of it is to ignore it. Spinoza argued that we should never feel depressed, or sorry about anything we have done or that is done to us, since this makes us even more miserable. That results in our becoming more passive, and so more unhappy, and this is a highly self-destructive process. He thought that we should observe the effects of our feelings on us and try to redirect them in a way which results in their becoming more positive. Easier said than done, you might well think, but it might be that he would say it is part of a process, and this is how we should start, by doing all we can to pay attention to what is happening to us and then taking steps to alter our reactions.

No, a lie is when you tell someone that something is true knowing that it is not. In this case you merely produced a false statement.

There used to be a popular argument in philosophy just like this, and clearly as you say there are similarities between ethics and aesthetics. I don't think that aesthetics is about what we should enjoy to perceive, though, since there are many things we think we ought to see but certainly do not enjoy seeing. As you say, people may disagree about value judgements, and often do, but that does not show they are not true and objective. People disagree about all sorts of things, after all. There are certainly some works of art which I could understand people not appreciating, but others which I could not. Similarly, if someone said that he thought it was alright to kill someone because the latter had annoyed him, I would not know what to say. A lot of urban murders do take place for precisely this reason nonetheless. It is difficult to think there is not something objective lurking in these value judgements, but precisely how to identify it is very difficult to understand.