I've just read through this quickly and wanted to point out something frannyandzoey said.
"I don't like methods such as time out and rewards and I don't think they are respectful or generally helpful, for me (I have used them myself, when losing the plot, or can't see another way forward)"
Imo, that is what things like time out/rewards etc are used for, when there is no other way, which nomally, there is. If we can keep these methods as a last resort, then they can be useful, overuse can render them pointless though.
Dp can be quite quick to go for time out or some other form of punishment (tbf he is new to all this, he's only been stepdaddy for a year, yet I have been mummy for 7) I often find myself, not undermining him, because that is a root cause of many behavioural problems, but asking if I can butt in, and actually asking the children why they have done whatever they have done, or what the problme is.
DS is just about to turn 3 and he sometimes surprises me with how much he can explain his feelings. Children act a certain way because of a feeling, if you can get down to the bottom of what they are feeling and why, the behaviour can vanish as quickly as it started.
Something DS has started to say when he gets frustrated or fed up is 'argh, I'm so angry' through clenched teeth, which dp was really shocked about, and asked what I thought we should do about it, and tbh, I think that a 3yr old identifying anger or frustration and walking away from a situation is a good thing! so I will ask him for a hug and ask him what has made him angry.
I honestly think that if we encourage children to be aware of their feelings and let them know that all these feelings are perfectly normal and ok, then find them a way to help them deal with it there won't be anywhere near as much bad behaviour, and thats without punishments.