first off, when my supply goes a little low, i always let dd nurse first and then i'll pump a little. she too gets very frusterated when the milk doesn't come IMMEDIATELY but i try.. i know it's frusterating sitting there staring at a pump that doesn't pump anything, but it is helping. just try to relax, and u should get more soon enough(few days probably). i pumped alot in the beginning b/c i had an overactive let down and too full of milk, then i didn't pump for a few months b/c it was under control, then when i tried pumping again b/c i wanted to go out for a bit, my breasts didn't respond either, i think they need to get used to it again! but don't give up, u really are getting somewhere with the pump even if nothing comes out right now!
as i was advised by a mod, (i was also cluster feeding my lo in the evening) she said that at that age (ur lo isn't too much younger than mine..) they shouldn't be cluster feeding in the evening b/c their bellies aren't learning to sustain them for longer periods(through the night). i realize that i was making my dd a 'snacker' trying to up her calories also, and that makes for very long nights!! i do a dreamfeed as well..but if u go to bed that early that might be tough - but u could always try and do it right before u go to bed.
i also noticed u seem to have the same prob i do, my lo is now down to one feed during the night usually at 5am (i dreamfeed her at around 11pm), then she's not really that hungry when she first wakes up...i think in both of our cases it is a little bit of habit that they are waking out of..u might try water for the feeding right before the morning wake up feed, it will be digested quicker and his little tummy will be ready for a full morning feed! i did this yesterday and it worked pretty well but threw off our whole daytime routine b/c she didn't sleep till 8-8:30 and was up for the day at 7am...small price to pay to try to teach her to sleep through the night!
anyway, keep in touch and let me know how things are going, or if u have found any tricks of your own...pm sometime if u need!