Now, while How Stuff Works is generally a good site, there are some areas that they could have been clearer on. The paragraph

[Aren't there other aubatomic particles other than quarks?]

I always thought that the spin of a particle does not mean the particle is spinning like a top in physical space, but refers it as intrinsic angular momentum. The mathematics behind it behaves (I think) a lot like "normal" angular momentum of a top spinning but from what I have read, that is not what is meant by spin. I also have heard that it is impossible to measure its spin due to confinement.

Also, if the universe has a consistent basis on the same mathematical laws, then other variables can't be changed. Otherwise, the whole laws of mathematics would be off. In other words, if the universe has a progressive time which could be equated to a math problem being worked out, then even the smallest problems would have to obey the rules of the biggest problems. Correct?

I seem to fail to understand how this would apply to humans and their decisions, since the MWI only applies to subatomic particles. Any insight?

It's true that spin of a particle isn't much like classical spin, but you can certainly measure a particle's spin on a given spatial axis, using a stern-gerlach device for example, and you'll always get either the result "spin-up" or "spin-down" on that axis.

I don't understand what you mean by "other variables", or "progressive time which could be equated to a math problem being worked out", or what this has to do with the quantum suicide thought-experiment. Can you elaborate?

No, the whole point of the MWI is to assume that all systems obey the same quantum laws as individual particles, including macroscopic systems like us (which are after all just large collections of interacting particles). See here or here for more info.