Should Mendelssohn's "Spring Song" be played in slow or fast time?

It is marked "Allegretto grazioso." The latter term (graceful, in English) precludes a too-quick movement.

What a Dot May Mean

This is the seventh measure of Chopin's Polonaise, Opus 26, No. 1. What is the meaning of the dot placed after the D in the bass? Whenever this measure is repeated the dot occurs, or I should have thought it a misprint.

The left-hand notes follow each other as eighth-notes. Their respective duration, however, is indicated by the upward stems and the dot. It is intended here that a complete chord should be built up by accumulation, as in illustration a:

and I would also hold the fifth eighth as in illustration b.

Where the Accent Should be Placed

In playing Chopin's Impromptu in A-flat, Opus 29, should the first or the last note of the mordent receive the accent? I have heard the mordent sound like a triplet? Is this the correct accent?