Slippery Slope or Non Sequitur????

I have a thought that always bugged me. Isn't according to the non sequitur definition, every fallacy a non-sequitur? Since every fallacy is fallacious reasoning, that means that the premises does not support the conclusion. The only difference compared to the definition is the "very little" support, which is a totally subjective qualitative criterion. So, by definition isn't every fallacy a non sequitur? (or at least every fallacy that rely on some premises, that is exluding fallacies like Alleged Certainty, Style over substance, Proof surrogate, Argument by repetition etc, which are just claims without reasoning)

Pretty much. I consider the non sequitur the default fallacy when no specific fallacy fits better. I wouldn't claim that it fits all fallacies, but I will say I have yet to come across a fallacy where this wouldn't also fit (sort of like the Black Swan thing).

Every  formal  fallacy is a non sequitur, yes. And as Dr Bo points out, in Logically Fallacious we use that term when we can't think of a specific fallacy name. 

If we understand a non sequitur to be a "leap" in logic - jumping to a conclusion that the premises do not support - then all fallacies do come under that category.

[To TrappedPrior (RotE)]

What's the difference between informal fallacies with formal ones? Is there a specific criterion that a fallacy has to satisfy to be deemed a 'formal fallacy'?

Formal = Deductive
Informal = Inductive/Abductive.

[To Bo Bennett, PhD]

I remember the definition in the book that says that the conclusion of a deductive argument has to be true (if the premises are true), while inductive argument is merely based on possibility. So I can understand what deductive argument and inductive argument is but not what deductive fallacy and inductive fallacy is. So correspondingly to the deductive/inductive argument, a formal fallacy is reasoning that is (deductively) definitely fallacious while informal fallacy is reasoning that is most likely wrong? Because all inductive arguments could be possibly wrong. I also know that every fallacy is fallacious reasoning. I'm a bit confused. For example argument from age or all the other identity fallacies (appeal to norm, accomplishment, appeal to celebrity) these are just biases. I feel they're neither deductive nor inductive. Or weak analogy. Or non sequitur. Or No true scotchman. These are all examples off the top of my head that I cannot fit them into either category. 

The way I always remember it is that formal fallacies are contained in the form of the argument. If an argument can be generalized in a way that it could be expressed like a math equation or a venn diagram, it's likely a formal fallacy. For instance, all A are C, all B are C, therefore some A are B.