My suggestion is to not think of nursing every 2 hours, 3 hours, or any hourly scedule. Most babies do not get hungry or need to nurse on an hourly time table. They may nurse frequenlty for part of the day, and if they nurse frequently enough, the longer sleep stretches are not an issue. Rather, if you want to increase sessions, look at how many times in a 24 hour day baby has nursed and try to up that by a session or two.
Ways to do this-keep baby with you more, sleep in close proximity, you may find then that baby begins to cue more frequently. No need to wait for a cue at all, offer the breast as much as you like. Try bringing baby to the breast when baby is asleep, babies can and do nurse in thier sleep. If your baby will not start cueing more 'naturally' or nursing in sleep, I really don't see anything wrong with waking baby over a prolonged sleep stretch when trying to increase nurisng sessions or weight gain. The worst that can happen is baby will not nurse and you get less sleep. Not ideal of course, but it's not a problem beyond that. If baby absolutely will not nurse more than 6 times a day, I think adding a session or two of pumping per day may be warranted. I don't think you need to do it in the middle of the night, try to do it at times you would normally be awake. I also don't think you will have to do it forever, but if you are concerend about supply I would trust those instincts.
Also I would not worry about baby not drinking vigorously, noty seeming interested, etc. Babies nurse differently at diferent times. If he is at the breast and taking in milk, even for a short time, he's interested. Short but frequent feedings is a perfectly normal pattern.