Regarding the selling of blood, aside from the fact that giving a monetary incentive for homeless people and criminals to give blood is a REALLY bad idea, the best possible "reward" for giving blood is the act itself and to a lesser extent recognition. The empirical research on motivation is quite solid and it all definitely points to the fact that providing monetary or any other kind of incentives destroys motivation. If you wish to review the research, you can read Punished By Rewards by Alfie Kohn.
What happens is that output (blood-giving) will go up in the short term but then it will backslide to either the previous level or to a lower level. As soon as you put a price on an activity, you're signaling that that price is the value of doing that thing. And that price is almost certainly not going to be enough to motivate people. So where before people were giving blood because it was "the gift of life" now people are going to give blood because it nets them 10$. And let me assure you that much fewer people are going to do it in the latter case.
Regarding your first point, this is quite irrelevant. What you're neglecting is the fact that just means don't necessarily end in a just outcome anymore than a just outcome necessarily implies that it was arrived at by just means. The outcome is a STATE, and the means are a PROCESS. And properties of states aren't properties of processes. This is illustrated thus: living is a process that doesn't change your humanity, but you can become a corpse by living (a corpse is not a human), while being flash-frozen into an icicle won't stop you from being human.
Now, you're going to complain that dying is not a part of the process of living. Well you see, I'm going to turn this around on you and say that *retaining* the meat while someone is starving in front of you is not just. It doesn't matter whether the person gained the meat through just means. What matters is that any attempt to retain it is unjust. And this unjust means results in an unjust outcome: being able to lord it over someone who's starving to death.
> He did not earn it, luckily though, in all probability, he would get fed.
Not good enough. It's not good enough that "in all probability" he would get fed. It must be an absolute. And if you seriously don't see the injustice in this, then we have nothing more to say to each other because from my point of view you are morally corrupt.
By the way, there is absolutely no argument whatsoever, no justification whatsoever, no rationalization whatsoever, that you can make to say that you "earned" land. Or that you "earned" sunlight. Or that you "earned" air. Or that you "earned" language. Or that you "earned" our highly developed technological culture. And since you cannot have earned any of these things, and since ALL of them are inputs into getting that tonne of meat, you therefore, logically, cannot say that you earned that tonne of meat.
If you are genuinely curious about need then I suggest you study human rights. They come in a hierarchy of lesser and greater rights. The human right of the starving not to be exploited is far greater than the right to just hang onto some possessions. It's very different from ownership since it means, at a minimum, that
the "owner" MUST sell and that they MUST sell at a reasonable price.
Effectively, they can be expropriated.
Regarding responsibility, I suggest you study the countless cases where people are held not responsible for their actions. Let's start with children. We can pass through the intoxicated and get to the mentally handicapped. I don't think I should have to point this out.
As for your final example, it's a strawman. Money only has meaning within a society, and if a member of a society needs money for some clearly defined need then it should be the society as a whole that provides it (perhaps from the idle rich who are spending it on yachts) and not any individual person. But then, thinking about society as a whole is something egotists are not wont to do.