applepushserviced and ocspd takes a lot of memory, is killing them safe?
The OS handles unneeded processes automatically by swapping them out to disk while they are not running. You won't get significant amounts of memory back by killing them.

In addition at least ocspd is started automatically by OS X if needed. So even if you kill it, it will be started again as soon as Safari (or any other app) needs to verify certificates.