Assuming medical issues have been ruled out my guess is that bub is waking because of hunger. At 7.5 months I think it would be very difficult to sleep through if you weren't having a good amount of solids (to include plenty of protein and carbs). Until solid intake improves other attempts to help bub sleep *may* be futile. Of course I could be wrong however this is my best guess.If you think this could be a factor then I would look at moving at least some of the solid feeds before the milk feed. Or cut one of the afternoon feeds and replace it with a snack. It may take a few days before bub adjusts solid intake. Bub may be unlikely to increase solids while bub is still getting massive milk feeds through. Have you tried purées in addition to finger foods? One tip I found handy was for parents to watch their own facial expression. If mum has a concerned look (eg as the food is too hot) then bub may be turned off. Have a positive smile no matter what - even if you are feeding bub brussel sprouts
Can you local MACH clinic help with strategies for increasing solids?
My second guess is that temp may be a factor. How do you know what the temp is through the night? Do you have a gro-egg? Thermostats with baby monitors are notoriously inaccurate. At 20 degrees I'm not sure bub would be warm enough in the current bedding. At 20 I would place my boys in a legless long sleeve onsie and a 2 tog sleeping bag. Some bubs need an additional blanket. If your room thermometer is
Not accurate and the temp infact dips below 20 bub may likely be cold.
Third guess - habit. Bub may wake one night for a certain reason (teeth etc) and before you know it bub gets used to the extra attention and wakes from habit. My eldest did this with teething - woke 2 nights from genuine pain so I fed. Woke a third night from habit - I could tell he wasn't in pain- didn't feed. 4th night slept through. The longer a habit continues the harder it is to break. Be careful about holding off on night feeds though until bub is on solids.
Fourth guess - ditch the dummy and possibly the white noise. The dummy is especially notorious for impacting a bubs ability to self soothe/increase night wakings. Not always, but more often than not.
As mentioned previously I think solids is the key so would focus on that first.
Best of luck