Is your lo reacting at all to the yoghurt? Have you tried and dairy alternatives like hemp, coconut or oat milk with cereals? You can get Wot No Dairy yoghurt and violife is a cheese substitute.
For breakfast you could try eggy bread, scrambled egg, oatibix, Ready Brek or Weetabix mixed with oat milk, blueberry pancakes made with alternative milk, a banana split lengthways, toast with smooth nut butter [almonds are high in calcium]. Jus rol croissants are Dairy Free too and agree on hot cross buns. Try buttering them with Pure Sunflower spread.
How is his weight and length now? I'd be reluctant to introduce more solids at this stage unless there has been a very clear improvement.
Are you thinking of offering a mix of purees and finger food? Have a read of the MN weaning recipes. Things like the Baby Dahl and Banana-Cado are very easy and will be more nutritious than the jars.
For lunch how about offering some finger food, like a sandwich, pitta pizza made with violife, homemade salmon fish cakes, hummus with raw veg, and maybe offer some puree for pudding, like a mashed banana, or wot no dairy youghurt.
For tea, could you offer what you are having? You can either just give it on his tray or mash it if he would prefer. Just watch the salt levels. You can get low salt stock cubes from most places these days.
Rice pudding made with koko milk is very nice, the whole family should like it.
Good luck 