Upvoted, but as someone who, without quite being a total utilitarian, at least hopes someone might be able to rescue total utilitarianism, I don't find much to disagree with here. Points 1, 4, 5, and 6 are arguments against certain claims that total utilitarianism should be obviously true, but not arguments that it doesn't happen to be true.

Point 2 states that total utilitarianism won't magically implement itself and requires "technology" rather than philosophy; that is, people have to come up with specific contingent techniques of estimating utility, rather than just reading it off via a simple method which can be proven mathematically perfect. But we have some Stone Age utility-comparing technologies like money and the popular vote, and QALYs might be metaphorically a Bronze Age technology. I suppose I take it on faith that there's a lot of room for more advanced technology before we hit mathematical limits.

That leaves the introductory paragraph and Point 3 as the only places I still disagree:

In total utilitarianism, it is a morally neutral act to kill someone (in a painless and unexpected manner) and creating/giving birth to another being of comparable happiness (or preference satisfaction or welfare).

In hedonic utilitarianism, yes. Are you making this claim for preference utilitarianism as well? If so, on what basis? If we don't give credit for creating potential people, isn't most people's preference not to be killed enough to stop preference utilitarians from killing them?

And you also have to be certain that your theory does not allow path dependency. One can take the perfectly valid position that "If there were an existing poorer population, then the right thing to do would be to redistribute wealth, and thus lose the last copy of Akira. However, currently there is no existing poor population, hence I would oppose it coming into being, precisely because it would result in the lose of Akira." You can reject this type of reasoning, and a variety of others that block the repugnant conclusion at some stage of the chain (the Stanford Encyclopaedia of Philosophy has a good entry on the Repugnant Conclusion and the arguments surrounding it). But most reasons for doing so already pre-suppose total utilitarianism. In that case, you cannot use the above as an argument for your theory.

Can you explain this further? If we don't allow potential people to carry weight, and if we are preference rather than hedonic utilitarians, then the only thing we are checking when deciding to create all these new people is whether or not existing people would prefer to do so.

The fact that the repugnant conclusion has "repugnant" right in the name suggests that most people don't want it. Therefore if total utilitarianism is about satisfying the preferences of as many people as possible much as possible, and it results in a conclusion nobody prefers, that should be a red flag.

If existing people understand the repugnant conclusion, then they will understand it is a likely consequence of creating all these people is that the world loses most of its culture and happiness, and when we aggregate their preferences they will vote against doing so.

So I don't see what you mean when you say this reasoning "pre-supposes total utiltarianism". It presupposes people's intuitive moral preferences for a happy world full of culture to a just-barely-not-unhappy-world without, and it pretends we can solve the aggregation problem, but where's the vicious self-reference?