As far as the first question:
Why do malachim need a ladder? Can't they fly or have some other form of supernatural transportation?
I heard from Rabbi Shlomo Farhi quoting Rabbi Moshe Weinberger the following:
The Gemara in Chagigah 13b writes:
כָּתוּב אֶחָד אוֹמֵר: ״שֵׁשׁ כְּנָפַיִם שֵׁשׁ כְּנָפַיִם לְאֶחָד״, וְכָתוּב אֶחָד אוֹמֵר: ״וְאַרְבָּעָה פָנִים לְאֶחָת וְאַרְבַּע כְּנָפַיִם לְאַחַת לָהֶם״? לָא קַשְׁיָא: כָּאן בִּזְמַן שֶׁבֵּית הַמִּקְדָּשׁ קַיָּים, כָּאן בִּזְמַן שֶׁאֵין בֵּית הַמִּקְדָּשׁ קַיָּים. כִּבְיָכוֹל, שֶׁנִּתְמַעֲטוּ כַּנְפֵי הַחַיּוֹת.
One verse states: “Each one had six wings; with two it covered its face and with two it covered its feet, and with two it flew” (Isaiah 6:2), and another verse states: “And every one had four faces, and every one of them had four wings” (Ezekiel 1:6). The Gemara answers: This is not difficult, as here, when the verse states they each had six wings, it is referring to the time when the Temple is standing, while there, where four wings are described, it is referring to the time when the Temple is not standing, for it is as if the number of the wings of the animals were diminished so that they now have only four.
In other words, the melachim who only had four wings were present in the time of exile, a time of churban, post the Beis Hamikdash (see Rashi).
The Gemara continues:
הֵי מִינַּיְיהוּ אִימַּעוּט? אָמַר רַב חֲנַנְאֵל אָמַר רַב: אוֹתָן שֶׁאוֹמְרוֹת שִׁירָה בָּהֶן.
Which of the wings were diminished? Rav Chananel said that Rav said: Those with which they recite song.
The mefarshim ask which wings do they use to recite their song? And they answer it's the ones they fly with.
Explained Rav Farhi, even angels, spiritual beings, when they experience churban they lose the ability to fly.
Applying this to the case of Yaakov. Yaakov was in the middle of immense trauma. He was fleeing to the unknown, from his twin who was hell-bent on murdering him. This trauma, this vulnerability as his whole world was being knocked down impacted on the angels who lost the ability to fly.