Even before I got past your first couple of sentences I was thinking, "needs to eat more during the day," and that seems to be what's going on from reading the rest of your letter.
It partly depends on how long this has been going on and whether you are committed to increasing his day and solid food intake. If he was 7 weeks old, I'd say let him nurse at night to increase supply. But at 7 months, he really needs to be working towards getting more from solids, right?
My older son went through the same thing, same age (7.5 months, I think), except he was weaned by then. I really think the only answer is to cut back on the nighttime feedings and increase feedings during the day. We were able to do it by cutting formula with water at night (eventually going to water-only bottles.) If he will take a bottle, you might start trying to replace some of those night-waking feedings with water. Within 3 days we had cut nighttime bottles to water only and by the end of the week my son was eating a lot more during the day and waking only once or not at all at night.
He was also a skinny one - 10th percentile weight and 90th height - but my pediatrician also supported getting him to eat more solids and more during the day. You may want to ask your pediatrician too, if you need the moral support. It was actually a lot more painless than I expected because we did it gradually over a few days. Good luck!