When you calculate a probability for each of two alternative outcomes of an action, you do not answer the question "Which of the outcomes do you think that the action will cause?" To decide the altruism of your potential actions, answer the question. Rely on a specific prediction of the future or specific understanding of the past or present.
Consider a coin toss. You are tossing the coin. Suppose you credit lack of ability or knowledge as the reason you don't choose outcomes of coins that you toss. You try to compensate for this lack. You start your coin toss with the head facing up. From past observation of your coin tosses, you expect that each spin in the air will average 0.05 seconds. You want to grab the coin underhand in about 1.025 seconds before you flip it over onto the back of your other hand to show heads. You have been practicing, and have reached a 70% probability of getting heads on a coin toss that starts with heads. With each practice session, you are sure that your coin tosses will come up heads if they start heads. You are puzzled about why you have been wrong 30% of the time over the last two weeks.
If you believe that your action is a sufficient cause of a consequence, then for you, that outcome has 100% probability, given your action. You don't have to know why your action causes that consequence in order to hold the belief in that cause. Of course, you don't have to believe that an outcome has 100% likelihood of occurring in order to believe that your action is a sufficient cause of it. We have plenty of beliefs that are not consistent with each other or with evidence. The irrationality of believing in an action's consequences is not a concern once you begin altruistic value calculations for those consequences. You just need to arrive at a belief in some consequences of your actions first.
It's easy to acknowledge that what you believe will happen has a low probability. It's much harder to continue action with the belief that your action fails to bring about its intended consequences (its purpose). Expected value calculations don't seem to faithfully represent a person's internal sense of conviction that an outcome occurs. Or else opportunities with small chances of success would not attract people. In those cases, the report of knowing that there is a low probability of success is irrelevant. In fact, that person reporting the small probability of success might have another purpose in mind that their action seems destined to fulfill, whether that purpose involves their process or just a different end result.
As an aside, some people are attracted to simple, clear, and vivid representations of possibilities. Such representations create a sense of reality to a possibility. People can also enjoy the process of pursuing a purpose. That is, in pursuit of the unlikely that is ostensibly attractive, they might also be having fun. Seeking fun is sometimes an unacknowledged purpose behind claimed counterintuitive or unlikely purposes.
If you believe that your action is a necessary cause of an outcome and that the outcome will occur if you perform your action, then you believe that the outcome is a consequence of your action. Assign an altruistic value to that consequence, no matter how small the probability you assign to that outcome. Given two outcomes that your action is necessary to cause, outcome A (that has a 70% probability) and outcome B (that has a 30% probability), you can expect that either will happen depending on what you believe about the specific additional causes of A and B present in a particular instance, or just because, and not know why.
It is your decisions from instance to instance that will reveal your altruistic value calculations to you, that is, the consequences you considered and how you scored them and compared them across alternative actions. I started off with a proposal for a numeric scoring system that represents mathematical intuitions about scale and allows quantitative comparisons using distance calculations. However, the fundamental process that I proposed is just a formalization of going through your life and counting up the altruism and anti-altruism that you caused, whether intentionally or not.
Respect that your altruistic value calculations will always be subjective. You have no guarantee that consequences you believe in are actually consequences. Use belief in consequences for score, scale, and distance calculations because those beliefs are what you have.
If I add probability weights to outcomes and score those outcomes for their altruistic value, then I am deviating from how I think about consequences. My calculations will not mirror my intuitive judgements. The outcomes I consider will not have altruistic value that I "caused." I will not appreciate my own actions from the perspective of believing that I cause, and can intentionally cause, external events through my actions. The absence of that perspective will deny me access to my own beliefs about what my actions cause or control. Therefore, it is necessary to perform altruistic value calculations from the perspective that my actions have consequences and purposes, not just correlation to outcomes.
In conclusion, to believe that "My action has a consequence X" is more than to believe that "An outcome X has a probability Y given my action". My initial Red Team Contest post proposed a specific process and some benefits. Those benefits will not flow from expected value calculations.