Re: Do I need to work on my supply?
Nothing on your list of concerns sounds like anything to worry over. Your baby isn't taking much by bottle on that one day per week when he's home with your DH. If that were the case every day of the week, you might have an issue, but since it's just one day I wouldn't consider it to be a big deal. I'd guess that your LO has decided he prefers to get his milk at the breast, and is willing to wait until you get home. It's like someone who goes to a restaurant, and finds that there's a line out the door. The maitre d' says "Hey, you're a good customer and we'll make you a to-go order so you don't have to wait for a table", but his response is "No, I'd rather have the meal AND the atmosphere."
Short nursing sessions are very normal with an older baby. They become efficient feeders and they also become more interested in the world, and less interested in long periods of comfort nursing.
3 oz is normal pumping output. Most moms produce about 1.5 oz per hour when their supply is well-matched to demand.
Getting your period back is normal and not a problem unless you find you're unable to pump enough milk to satisfy baby's needs
Occasional dry or minimally wet nappies are normal; older babies often learn to hold their urine for longer time periods.
Less night-nursing is not a problem as longs baby is getting enough during the day, and it sounds like your baby is, since he's generally nursing about 8x per day, and having decent nappy output and weight gain. Feeling flat, deflated, or soft is also normal as long as all the preceding conditions apply.
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!"