According to TM, page 216, escape pods have room for 6 people - you have to read the fluff. TM, page 227 has the lifeboat, and it fits 7 people.
While I think the Essex is particularly low on the lifeboat/escape pod count, I wouldn't be surprised if the designers assumed a high casualty rate before "abandon ship" was called. Personally I'd put the number around 50%, but I usually build my ships to have lifeboats/escape pods to get 90-100%+ the crew because abandoning a ship doesn't always happen during or immediately post combat.