Excellent question. J.S. Mill regarded the Greatest Happiness Principle as the moral truth. The principle states that "actions are right in proportion as they tend to promote happiness, wrong as they tend to produce the reverse of happiness." Mill then equated happiness with pleasure, following Benthamite tradition. After all, both Bentham and Mill are ...
While the question is an interesting one, there are several issues at hand to consider. First, the question seems premised on the belief that there can be multiple categorical imperatives. This is not Kant's view of the matter. For Kant, there can be multiple hypothetical imperatives but only one categorical imperative (not all contemporary Kantians agree). ...
The early works
Kant gives multiple explanations for why lying is wrong and these accounts differ. In Kant's earlier works, Kant gives several different arguments against lying. Arguably the first in the Groundwork occurs before he even articulates the "Categorical Imperative" when discussing actions, he considers why a shopkeeper should be honest. Kant ...
From a utilitarian standpoint lying is not wrong in and of itself. It can be justified as morally acceptable if the greatest good for the greatest number of people produced by promulgating an untruthful statement outweighs the bad (i.e. living in a society where information is unreliable).
It is a difficult argument, from the utilitarian standpoint, for a ...
The issues you list -- altruism, reciprocation, etc... -- are not specifically sexual, but are general ethical issues and therefore would be discussed outside of sex. Philosophers prefer general principles to specifics, so instead of studying sexual selfishness, they would study selfishness in general.
Which probably makes philosophers lousy lovers :)
Kant already responded to this same thought experiment.
ON A SUPPOSED RIGHT TO TELL LIES FROM BENEVOLENT MOTIVES. 1 - Immanuel Kant, Kant’s Critique of Practical Reason and Other Works on the Theory of Ethics 
I myself have wondered why I have come across so little discussion of sex among philosophers, especially since it seems to me that it would be a very serious question for ethics and philosophy of religion (i.e. why do sexual norms vary so much from society to society? Why are some religions so hung up on trying to control sexual behavior?).
If there is ...
What is happiness or pleasure???
Depending on the answer, you question can be either meaningful or meaningless. Philosophers have offered at least four different answers.
happiness = hedonistic pleasures
Problem: Those who seek these pleasures eventually became unhappy. too much gluttony leads to health problems.
happiness = desire satisfaction
To understand, does not mean to forgive.
Let's go to definitions of Empathy:
Empathy is the capacity to share or recognize emotions experienced by another sentient or fictional being.
Ethics, sometimes known as moral philosophy', is a branch of philosophy that involves systematizing, defending and recommending concepts of right and wrong ...
There are a few concerns here.
Does the document you describe actually have the properties you describe? Indeed, can any document at all have them?
Should you believe in the specific claims of the statements you're describing, supposing that it actually does have the properties you describe?
Should you in any case do A, B, C and refrain from X, Y, Z?