I've never added milk powder to mine, but I think I'll give it a go now as yours looks lovely!
As Daniel said, the milk can make a huge difference. I don't have access to locally produced milk, but I've found that one of our local shops sells milk from a smaller producer which doesn't seem to have been as heavily processed, and does make better yoghurt. If it's too thick, you could always cut down the time in the propagator?
In terms of cultures, Aldi sell a lovely Greek yoghurt which I buy every few weeks for a fresh start. It doesn't say on the container that it's live for some reason, and is very like 'Fage' but much cheaper.
I have a yoghurt maker (with variable temperature), but I've tried all different ways (flasks, scalding/different recommended temperatures/times etc.) and now I just whisk my starter into milk straight from the fridge, push the button and walk away. It looks like you've found a system that works well for you, which is great.