When to Harvest??

I must admit I'm having a little trouble deciding when to harvest my cool crop garden..it is May 22, and the heat is now turned up.. But, I wasn't able to get my plants in the ground till April 1. This means they've only been in the ground 52 days!! My Cabbage tag says 75 days till maturity. Now I'm ok with the cabbage situation, I've been growing cabbage for many years and know by eyeing them when their ready. But.. this year my cabbage plants are HUGE!!! I mean there quite lovely, large pale green beauties, but I've never had a cabbage that large before?? So I'm wondering when they are going to start to head? Maybe I got a mammoth variety or something and I didn't realize it? I'll have to look into that. The tag says, Bonnie Hybrid..Bonnie's Best Cabbage. Now the Kale and Romaine I'm a total newbie to growing.. Please Help!! The tag says romaine lettuce. Now working in a restaurant I've seen my fair share of romaine lettuce and made more than 100's of Caesar salads. This plant looks nothing like romaine lettuce... What?? Were the plants mislabeled? They clearly look like lettuce, just not romaine?? What to do? My neighbor keeps asking me when I'm going to harvest my lettuce, and I keep saying I'm waiting till it looks like romaine?? LOL...I think I'm going to go ahead and cut some of the lettuce maybe it was mislabeld..
My Kale is Winterbor Kale and says 60 days till maturity..so that's only a week a way. It doesn't look as big as I thought it would??
My Cabbage Stats..

Light: Full sun

Head size: 5 to 7 pounds

Matures: 75 days

Plant spacing: 24 inches apart

Plant size: 18 inches tall, 24 inches wide

Bonnie's best cabbage. Grows large, round, blue-green heads. Well suited to the South as a spring and fall cabbage. It is also performs well in the North as a summer cabbage.
Resistant to Fusarium yellows and tolerant of black rot.