I'm not sure I fully understand your use-case here. Elasticsearch only stores data in UTC, so converting to EST doesn't make sense. If you want to convert to UTC, add the timezone field to the timestamp processor, so it knows the time is in PST and to convert it to UTC.
The layout listed on the docs is actually a Golang time thing, and requires those specific time values.
Try changing your layout value to be 2006 Jan 02 15:04:05:999 and see if that works.