Re expressing. I don't know if this will help anyone, but this is my experience of it. At the start it was much harder than I'm now finding it. I couldn't get anything at all until 4 days in and that first week after felt really frustrating, as I didn't feel like I was getting anywhere with it and it was a battle to get enough both psychically and mentally.
In terms of how much; at 9 days DS would have about 30mls per feed of expressed milk. We've gradually increased it so he's now up to 70mls a feed at 20 days old. He was feeding every 3hrs (slightly longer at night), but this has become more frequent too now so its more like 2 and a half hours during the night and day and 1 and half hours in the evenings when he has a bit of a frenzy.
There is a calculator for how much expressed milk you need kellymom.com/bf/pumpingmoms/pumping/milkcalc/ here, but at this stage (under a month old), its not terribly useful; the useful bit of information on that page is actually below the calculator where it shows the maximum capacity of a baby's stomach (bare in mind that breast feed babies have a slightly smaller capacity than formula feed ones - so if you are combination feeding or ff they eat more).
At 9 days I wasn't getting much more off than 30mls when I was expressing. Maybe 40mls at a push. But by being incredibly strict about expressing regularly (roughly once before DH goes to work, once during the daytime, once when DH gets back from work, once at bedtime around 10pm and once in the night) I've managed to gradually increase how much I'm getting off. It does feel never ending and like I'm either attached to a machine or feeding him with the bottle constantly though, so its hard, hard work, but it does feel like it is now starting to pay off. I'm still having to be religious about it, but its beginning to feel routine rather than forced. It is a team effort between me and DH though; I couldn't do it, if DH didn't take the strain and look after DS when I need to express.
DS is doing well on what has been almost exclusively expressing milk without tops ups of formula and has started to gain weight, after initially dropping a bit. I've not pushed breast feeding at all, but the expressing has given my nipples a break, but still toughened them up and changed their shape. DS has in the past week occasionally started to take straight from the boob without too problems which is a revelation as it just wasn't happening before - we've changed nothing. Its been so much less stressful. I tried desperately to get him on at first, but it wasn't happening so just gave up and concentrated on expressing. But I gave it a couple of tries and it just sort of happened naturally; I think haven't the pressure taken off, by knowing that I didn't have to helped a lot. I am doing this more now as obviously its less of a faff. I still get sore, but no where near as much as I was. Fingers crossed I can do it more frequently.
One of the tips I've heard is if you are breast feeding to pump for 5 mins per boob after you have feed the baby as this increases your supply and its easier to get off and pumping in the night helps as middle of the night feeds regulate how much you produce more than daytime feeds. (FWIW, If I pump after feeding him straight from breast, I don't get much more than 30mls off.)
Another thing, I think have found interesting is I'm using two different electric pumps; I'm finding they are very different and are effective differently in getting off milk because they pump in different ways. Which is a bit nuts! So I do think what pump you are using, does make a big difference. One might suit you better than another.
At the moment, I'm getting more off than he is eating and have been able to stockpile a small amount in the freezer. I just smell of cheese constantly now!
Honey, my words of wisdom for your DH going back to work are simply this; don't do anything but stay in bed/on the sofa and feed/change the baby for the day. Just get through it. It will be ok but you just need to survive the first day and get the confidence that you can survive.