rules or guidelines?

1) The Torah writes that if you have a large amount of ma’aser sheni produce to bring to Yerushalayim you can convert it to cash and bring money instead.  “Ki yirbeh mimcha ha’derech ki lo sochal se’eiso ki yirchak mimcha hamakom… ki y’varechicha Hashem Elokecha.” (14:24).  Rashi comments on ki y’varachicha – “she’t’hey hatevu’ah merubah la’seis.”  The words of the pasuk itself tell us that we are speaking of a case where the farmer is blessed with too much to carry -- what is Rashi adding? 

Maybe there is a better answer, but what came to my mind is the machlokes between the Rashbam (Baba Basra 122) and the Chasam Sofer (Shu”T Y.D. 234, see here point II) whether having a portion of land closer to Yerushalayim is better, since Yerushalayim is the holiest place, or whether having a portion further away is better because then one gets more schar for travel.  Rashi is perhaps emphasizing that the bracha the pasuk is speaking of is davka having so much fruits, but the fact that you live far from Yerushalayim, “ki yirbeh mimcha ha’derech,” and have to shlep everything to get there and maybe earn extra schar for the journey, is not itself a bracha.

2) “Al kein ani metzavcha leimor, ‘Paso’ach tiftach es yadcha…’” (15:11).  Rashi: “eitzah l’tovascha anu masi’acha.”  True, there is a seemingly unnecessary “leimor”  (see Gur Aryeh), but nonetheless, how can “metzavecha” be interpreted to mean good advice?  Doesn't the word “tzivuy” mean a rule, not a guideline?