Your pace looks fine for your easy runs - the point of
these is recovery, so as long as your form doesn't
degenerate into something that doesn't remotely resemble
your normal running stride, I don't think its possible to
run "too slowly" on your easy days.
You might think about about pushing the pace up slightly
on your longer runs (while still keeping your heartrate
within the desired range). The main reason I suggest this
is that at some point time becomes an issue on longer
runs - running for more than 2 1/2 hours is stressful
on the body, no matter how slowly you do it. I don't
know if your long runs are long enough for this to be
a factor, but I know for me that keeping the long runs
within a reasonable time frame makes recovery quicker
and easier - even if I run slightly faster to do so
(but still at an easy aerobic pace).