If your son is going straight back to sleep after he wakes for a feed, that is absolutely terrific, and gradually he might not wake up so often! Keep up the good work, and accept this is just going to carry on for a little while.
Mine had bad colic and would wake up for hours at a time all night. He didn't start sleeping through the night until recently and he's two years old this month! I know others who have had it even worse. I went back to work when he was a year old, and it was really hard on broken sleep - really, really hard. But, that said, its full-on work with a young baby and sometimes difficult to nap on their schedules anyway - so its hard even staying at home if you don't have help.
I would suggest trying to see if you can delay going back to work as long as possible, or work part-time for a bit. If not, you'll find you'll have to go to bed each night around 8pm in order to cope. You may need to do that anyway... (took me ages to do that, as I used to love my late nights!)
I know some lucky people who's babies start sleeping through as early as 3 months, but that's seems the earliest it can be expected... My friends who have managed that have had really calm lives, not much traveling, have had strict routines with their babies, and stayed home a lot in order to cater for the routines etc.
The thing about pumping and asking your husband to have a go is tough, because you've got to keep up your milk supply and will need to pump when he would normally have his feed... you could try pumping like crazy in the morning when supply is usually greatest, but it might be a bit tough to expect to produce enough for him all night and enough for him right then too... if you do manage to do anything in particular that seems to work, let us know!!
Good luck and have fun - the cuddly baby days fly by so fast!