seudas havraah; halacha k'divei ha'meikil b'aveilus vs safeik derabbanan l'kula

Rashi tells us, echoing the Midrash, that the lentil soup that Yaakov prepared was ובישל יעקב עדשים להברות האבל.  Chasal Sofer and others ask: the din is that seudas havraah must come from someone else; the aveil cannot use his own food.  אמר רב יהודה אמר רב אבל יום ראשון אסור לאכול לחם משלו (Moed Katan 27b).  Yaakov was a poor kollelnik who was someich al shulchan aviv -- he lived with his parents and did not have his own job or means of support.  How then was he able to make a seudas havraah for his father?  The meal he prepared was Yitzchak's own food!

Aruch haShulchan (Y.D. 378) writes that the chiyuv seudas havraah applies specifically to eating bread:

ונראה דהעיקר הוא הלחם, כלשון הכתוב. וכן לשון הגמרא שם: אסור לאכול לחם משלו, עיין שם. אבל תבשילין יכול לאכול משלו. וכן המנהג שמביאין להאבל לחם וביצים בלבד.

If so, it could be that Yaakov did serve Yitzchak's own food, and the real kiyum of seudas havraah was in eating bread from someone else.  (I would say it's still ktzas kashe to explain the words להברות האבל in Rashi.)

If this Ah"S is correct, it means aveilim have to be careful to make sure to wash before shekiya of that first day of aveilus to fulfill eating the seudas havraah (assuming the chiyuv is on them to eat, as opposed to the chiyuv being on others to offer them food.)  

I saw R' Shternbruch (Shu'T Teshuvos v'Hanhagos III:380) quoted as holding that even though the S"A paskens like most Rishonim that the chiyuv seudas havraah applies only to the first meal eaten, one should, if possible, be machmir like the minority view that holds all meals eaten in the first day (note the gemara's language: אבל יום ראשון) should come from someone else.  

He says a bit of lomdus and distinguishes between the din of safeik derabbanan l'kula and halacha k'divrei ha'meikil b'aveilus.  Sfeika derabbanan l'kula is an allowance to follow the more lenient view, but the issue remains unresolved; therefore, a person certainly deserves and gets credit for going the extra mile to be machmir.  Hilchisa k'divrei ha'meikil b'aveilus is because we do not want a person to engage in excessive mourning where there is no need to do so.  In these cases, you don't get extra credit for taking on more grief.

Halacha k'divrei ha'meikeil b'aveilus, R' Shternbruch argues, only applies to the nihugei aveilus like not washing, not wearing leather shoes, etc.  The din of seudas havraah is not a din in aveilus, but is done either 1) because we are afraid the aveil would be so consumed by grief that he would forget to eat, or 2) as an expression of nechama.  The reason we follow the lenient view and only require one meal is because of the din of safeik derabbanan l'kula.  Therefore, there is certainly something to be gained in this case by covering all bases.