Re: Possible foremilk/hindmilk imbalance?
My understanding is that if you're feeding often, on demand, then you really don't need to worry about the imbalance issue. 6 week olds want to eat all the time. That's normal. Not being able to put him down is also normal. Have you tried some kind of carrier so you can get stuff done around the house and go on walks? The fussiness may or may not be normal as well. it may be cured by carrying him.
Do you have OS/OALD? that might be a good reason to try block feeding. If I were you I would focus on getting him weaned off the shield (and i know others will join in here with some links from kellymom, please?) and stop worrying about the foremilk/hindmilk issue.
You are pumping A TON. Like, many moms only get 2 oz from a pump, total. This will be fabulous for your freezer supply (check now to make sure you don't have lipase). It's not "too much" unless it's causing other problems, and so maybe you do have OS and don't need to wrry so much about trying to pump after using the shield.
Nursing, pumping, cloth-diapering, babywearing, working professor mama with the awesomest SAHD ever.