how to prepare to survive in Lavan's house; "ain m'arvin simcha b'simcha"

1) Yaakov was told by his parents to go to Lavan's house to find a wife.  Why did he diregard his parents instructions and stop off for 14 years to learn by Shem and Eiver?  What happened to the mitzvah of kibud av?

R' Yosef Sorotzkin answers  that in order to survive in the environment of Lavan's house Yaakov had to fortify himself with non-stop Torah study for those 14 years.  This was an an abrogation of his mitzvah of kibud av, but rather a necessary step in order to be able to fulfill his parent's instruction.  

2) The Midrash writes on the opening of our parsha:

רַבִּי שְׁמוּאֵל בַּר נַחְמָן פָּתַח (תהלים קכא, א): שִׁיר לַמַּעֲלוֹת אֶשָּׂא עֵינַי אֶל הֶהָרִים, אֶשָּׂא עֵינַי אֶל הַהוֹרִים לְמַלְפָנַי וְלִמְעַבְּדָנַי. (תהלים קכא, א): מֵאַיִן יָבוֹא עֶזְרִי, אֱלִיעֶזֶר בְּשָׁעָה שֶׁהָלַךְ לְהָבִיא אֶת רִבְקָה מַה כְּתִיב בֵּיהּ (בראשית כד, י): וַיִּקַּח הָעֶבֶד עֲשָׂרָה גְמַלִים וגו', וַאֲנִי לֹא נֶזֶם אֶחָד וְלֹא צָמִיד אֶחָד. רַבִּי חֲנִינָא אָמַר גָּדוּד שִׁלְּחוֹ. רַבִּי יְהוֹשֻׁעַ בֶּן לֵוִי אָמַר שִׁלַּח עִמּוֹ, אֶלָּא שֶׁעָמַד עֵשָׂו וּנְטָלָהּ מִמֶּנּוּ. חָזַר וְאָמַר מָה אֲנָא מוֹבֵד סִבְרִי מִן בָּרְיִי, חַס וְשָׁלוֹם, לֵית אֲנָא מוֹבֵד סִבְרִי מִן בָּרְיִי, אֶלָּא (תהלים קכא, ב): עֶזְרִי מֵעִם ה'. (תהלים קכא, ג): אַל יִתֵּן לַמּוֹט רַגְלֶךָ אַל יָנוּם שֹׁמְרֶךָ, (תהלים קכא, ה): הִנֵּה לֹא יָנוּם וְלֹא יִישָׁן וגו', (תהלים קכא, ז): ה' יִשְׁמָרְךָ מִכָּל רָע, מֵעֵשָׂו וּמִלָּבָן. (תהלים קכא, ז): יִשְׁמֹר אֶת נַפְשֶׁךָ, מִמַּלְאַךְ הַמָּוֶת. (תהלים קכא, ח): ה' יִשְׁמָר צֵאתְךָ וּבוֹאֶךָ, וַיֵּצֵא יַעֲקֹב.

What was Yaakov's safeik of מֵאַיִן יָבוֹא עֶזְרִי ?  

The Ben Ish Chai explains that a person can be saved by Hashem b'derech ha'teva or b'derech nes.  He compares these two approaches to a father who gives his son an allowance and the son must decide how to spend the $ to manage his needs vs a father who pays all the bills and the son does not even need to carry a wallet.  Yaakov Avinu had bitachon that Hashem would save him, but he did not know how it would happen.  Would Hashem give him the wealth and resources needed and he would have to manage his affairs, or would his salvation be miraculous, without his having to take care of anything?  When Yaakov realized that he was penniless and had no ability to do anything for himself, he accepted that his plight was b'yad Hashem alone, and he would have a miraculous deliverance without having to worry about his own needs.

We once discussed the story of (Kesubos 62) Rebbi's son who went off to learn for any years and came home to find his wife was incapable of having children.  The gemara goes through Rebbis' thought process: could his son divorce his wife?  Could he take another wife?  Finally Rebbi came to the conclusion that there was no fair solution other than for him to daven for his daughter in law to be cured and be able to have children.

Why does the gemara go through the whole shakla v'terya of Rebbi's thinking?  If Rebbi knew he could daven and cure his DIL, why didn't he just do that?

This is the same yesod of the Ben Ish Chai.  It was only when Yaakov realized that he was penniless, that he could not do it himself, that he threw all his eggs into the basket of reliance on Hashem and his salvation came derech nes.  So long as there was even a hava amina that Rebbi's DIL would have a yeshu'a b'derech ha'teva, his tefilah would not have worked.  It is the realization that things are 100% b'yad Hashem that beings about a salvation.

3) It's interesting that the Rambam in Ishus 10:14 quotes the source of אין מערבין שמחה בשמחה  from our parsha:

. ואפילו בחולו של מועד אין נושאין נשים כמו שביארנו לפי שאין מערבין שמחה בשמחה שנאמר מלא שבוע זאת ונתנה לך גם את זאת

Tos (Moed Katan 8b) points out that this source is quoted in the Yerushalmi, but not in the Bavli.

The Rambam in hil Yom Tov 7:16, however, writes as follows:

אין רואין את הנגעים במועד שמא ימצא טמא ונמצא חגו נהפך לאבל. ואין נושאין נשים ולא מייבמין במועד כדי שלא תשתכח שמחת החג בשמחת הנשואין. 

If I just stop the quote there it seems like the Rambam does not hold of אין מערבין שמחה בשמחה at all.  Instead, the reason for not getting married on Y"T is  שלא תשתכח שמחת החג , or as the gemara in MK puts it, מפני שמניח שמחת הרגל ועוסק בשמחת אשתו.  

The Rambam then continues in that same halacha:

אבל מחזיר את גרושתו. ומארסין נשים במועד. ובלבד שלא יעשה סעודת אירוסין. ולא סעודת נישואין. שלא יערב שמחה אחרת בשמחת החג:

Here he does quote the din of שאין מערבין, albeit without quoting a source like he does in hil ishus.

See Lechem Mishne for starters to unravel what is going on here.