As for setting the survivor ratio, look at the GC data you posted. What is the ratio of the young generation size before GC and the largest size after GC? The after GC size is entirely within a survivor space. I would assume a max survivor space size of about 1.5 times the largest after GC size you see (1.5 x 36MB ~= 50MB), then 1278MB / 50MB ~= 25, which is what I would set the ratio to.
You need to also set the tenuruing threshold. These white papers might help:
Java Garbage Collection Statistical Analysis 101
Java Garbage Collection Performance Analysis 201
at http://www.cmg.org/cgi-bin/search.cgi?q=java+peter+johnson&x=30&y=10