Re: Sippy cup
I don't think there's any need to hurry the transition from bottle to straw cup. If your baby is comfortably taking a bottle at daycare, let him continue. He's not even a year old yet, and it's more important than he gets his milk than that he get it in a certain type of container.
I definitely wouldn't pump and offer straw cups all weekend long to hurry this transition. Especially when you're already struggling to get enough milk. The pump isn't as good at emptying you out as the baby is, and frequent and thorough milk removal is what builds and maintains supply.
How long as you at work each day? 15 oz might be appropriate, if you're gone about 10 hours.
Coolest thing my big girl said recently: "How can you tell the world is moving when you are standing on it?"
Coolest thing my little girl sang recently: "I love dat one-two pupples!"