Question: A surface read of Pirkei Avot and Hilchot De'ot would suggest that their contents appears to be primarily advice as to how one *should* proceed over and above the minimal halachik requirements. Nonetheless, these two respective works are codified among primarily halachik series, the Mishna and Mishna Torah respectively. 

Do the instructions provided in these two volumes (and other volumes that fit my aforementioned criteria) contain halachik weight for anyone or everyone? Are they codes to teach us how to behave should we wish to go beyond the letter of the law? Are they simply there to enrich our lives?

Answer: 
The first Mishna in Pirkei Avot deals with the chain of Mesorah, how the Torah was passed down from generation to generation, starting with Moshe at Sinai. Rav Ovadiah MiBartenura asks what's the relevance of this Mishnah to the rest of the tractate, which seemingly deals with ethics? He answers that this Mishnah was given as an introduction to let us know that even these seemingly 'ethical' commandments were also given at Sinai, and as such must be treated just like any other commandment given at Sinai.

That being said, your question is asking if these volumes 'contain halachik weight'. The short answer is yes, just like any other part of the Mishnah or Mishnah Torah. However, just like we don't conclusively rule Halachah directly from a Mishnah, we also don't conclusively rule 'ethical Halachah' directly from Pirkei Avot.
the torah is written in a universal form so that every Jew is able to fulfill it.

Nevertheless, G-d's intent is that those who can do more should strive to. This is known as the urge of the understanding.

The prescriptions in Pirkei Avot are in this category.

Most people are not able to fulfill all the words of pirkei avot, so it is not to be looked as 100% halachically binding. Nevertheless everyone at his level of understanding must try to fulfill whatever he can.

This is explained in the Chovos Halevavos, Gate 3 ch.3:

> 
> Third, the intellectual urge cannot include equally all who are under
>  the obligation of service, because some human beings are of limited
>  intelligence, while some are superior in understanding. But the urge
>  of the Torah applies equally to all who have reached the status
>  subjecting them to this service, even though they vary in their
>  understanding of it, as we have noted at the close of the first
>  treatise of this book.
> 
> 
> It sometimes also happens that an individual falls short in some
>  duties and exceeds in others. The intellectual stimulus varies in
>  different individuals in accordance with their capacity of
>  recognition. But the urge of the Torah is not subject to variation.
>  Its form is the same for the child, the youth, one advanced in years
>  and the old man, the wise and the foolish, even though the resulting
>  practice varies in different classes of individuals. And so Scripture
>  says in regard to the all encompassing character of the instruction of
>  the Torah for all the people, "Gather the people together, men and
>  women, and children, and the stranger that is within your gate, (that
>  they may hear and that they may learn and fear the L-ord your G-d . .
>  .)" (Devarim 31:12). Further, it is said, ". . . you shall read this
>  law before all Israel in their hearing." (Devarim 31:11).
> 
> 
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