I think you can perhaps actually infer the answer from the sources you yourself linked. Along with this, I would suggest that the latter halachot you link (regarding charity) suggest the intent of the former (regarding marital obligations):
אֵין פּוֹחֲתִין לְעָנִי הָעוֹבֵר מִמָּקוֹם לְמָקוֹם, מִכִּכָּר
בְּפּוּנְדְּיוֹן (הָרַמְבַּ''ם פֵּרֵשׁ שֶׁמִּשְׁקָל הַפּוּנְדְּיוֹן
הוּא ח' גַּרְעִינֵי שְׂעוֹרָה). מִד' סְאִין בְּסֶלַע. וְאִם לָן,
נוֹתְנִין לוֹ מַצָּע לִישַׁן עָלָיו וְכֶסֶת לִתֵּן מְרַאֲשׁוֹתָיו
וְשֶׁמֶן וְקִטְנִיּוֹת. וְאִם שָׁבַת, נוֹתְנִין לוֹ מְזוֹן ג'
סְעֻדּוֹת וְשֶׁמֶן וְקִטְנִית וְדָג וְיָרָק. וְאִם מַכִּירִין אוֹתוֹ,
נוֹתְנִין לוֹ לְפִי כְּבוֹדוֹ.
We give no less to a passing poor man than a loaf weighing a
pundyon... But if we recognize him, we give him according to his honor.
The sense is that the ironclad rules (of a pundyon loaf, mattress, oil, etc.) are for where we have no subjective information about what the person is actually accustomed to. If, however, we know the person and what they were accustomed to be fore they fell into hard times, we try to accomodate them based on what we know. Thus the famous gemara (Kethubot 67b) upon which the Shulchan Aruch's halacha is based:
תנו רבנן: "די מחסורו" - אתה מצווה עליו לפרנסו ואי אתה מצווה עליו לעשרו; "אשר יחסר לו" - אפילו סוס לרכוב עליו ועבד לרוץ לפניו. אמרו עליו על הלל הזקן שלקח לעני בן טובים אחד סוס לרכוב עליו ועבד לרוץ לפניו. פעם אחת לא מצא עבד לרוץ לפניו ורץ לפניו שלשה מילין
Our Rabbis taught: "...sufficient for his lacking" (Deuteronomy 15:8) - You are commanded regarding him to provide for him, not to enrich him. "in that which he lacks" - even a horse to ride upon and a bondsman to run before him. They said about Hillel the Elder that he took for one poor man from a wealthy family a horse to ride upon and a bondsman to run before him. Once, he did not find a bondsman to run before him, so he himself ran before him for three mil.
Similarly, with regard to a man's obligations to honoring his wife, since he presumably knows both his and her social standing, there is no ironclad rule that is applicable. If her socioeconomic status before the marriage was greater than his and she was used to finer things, that's what he would be obligated to provide. Likewise, if his status is socioeconomically greater, he has to provide her with what he is used to, even though she was used to less.
This is also the sense in Even HaEzer 89:1 that you link:
מֵתָה הָאִשָּׁה בְּחַיֵּי הַבַּעַל, חַיָּב לְקָבְרָהּ וְלִטַּפֵּל בְּכָל צָרְכֵי קְבוּרָתָהּ, וּבִכְלַל זֶה הָאֶבֶן שֶׁנּוֹתְנִים עַל הַקֶּבֶר. וְכֵן חַיָּב לַעֲשׂוֹת לָהּ מִסְפֵּד וְקִינִים, כְּדֶרֶךְ כָּל הַמְּדִינָה. וְאִם דַּרְכָּם לְהַסְפִּיד בַּחֲלִילִין, לֹא יִפְחֹת מִשְּׁנֵי חֲלִילִין וּמְקוֹנְנוֹת, אֲפִלּוּ עָנִי שֶׁבְּיִשְׂרָאֵל; וְאִם הָיָה עָשִׁיר, הַכֹּל לְפִי כְּבוֹדוֹ. וְאִם הָיָה כְּבוֹדָהּ יוֹתֵר מִכְּבוֹדוֹ, קוֹבְרִים אוֹתָהּ לְפִי כְּבוֹדָהּ, שֶׁעוֹלָה עִמּוֹ וְאֵינָהּ יוֹרֶדֶת:
If the wife died during the husbands life, he is obligated to bury her... Similarly he's obligated to provide for her a eulogy and lamentations as is the custom of the entire country. And if their custom is to eulogize with flutes, he shall not provide less than two flutes and wailers, even a poor Jew; but if he is wealthy, all is according to his honor. And if her hinor is greater than his, she is buried according to her honor, for she upgrades with him, but does not downgrade.
While their might be an ironclad minimum for even the poorest of the poor, once he/she transcends that, the eligibility is subjective and evaluated case-by-case using the norms of the country, era, and social standing.