Your attitude towards your own children seems to have no relevance whatever to Leviticus 26:29, or even to the whole chapter.
I woulkd disagree, enki.
As you point out in your post the second section 'deals with the punishments which God will mete out if His laws are not obeyed'. In other words, what follows is a list of consequences. Are any of them other than natural?
He even suggests that if they do not come to their senses, then He will punish them even more severely by devastating their lands and cities and scattering the remainder throughout other lands. In fact there seems to be a theme of hate running throughout this section.
As a parent, don't/wouldn't you hate it when one of your children wilfully disobeys you? Does that mean that you hate the child? It is simply God saying that he will progressively accept that, by their continued disobedience, the People of Israel were saying that they didn't want his presence or protection with all the escalating consequences that this passage lists. Remember that one can usually make the same impact on someone by actions of commission or of omission.
The fact that it is the longest section is no different to any other judicial document of the time, or even of today - laws, by their definition deal with wrong-doing.
However, I fail to see how your idea of a parent who either helps or, at least, doesn't interfere in the life of a wayward child has anything to do with a God who, according to this chapter, threatens to interfere by using vicious and appalling punishments for those who go against Him.
As I have said above and before, I don't see this passage talking about interference, be that vicious or protective, appalling or helpful. I see it as a list of consequences that will escalate naturally as a result of a people's continued and probably progressive rejection of God. God doesn't hav to actively punish us; all he has to do is leave nature to itself.
Hope, I am not talking about how we regard such things as natural calamities/wars/diseases etc. today. I'm talking about how the writer of Leviticus, in Ch.26, used them.
The writer of Leviticus either didn't think that they were just natural consequences or tried to frighten his readers into believing that they were God sent. The impression of God given here is of one who pursues active angry punishment in order to bring terror and distress to those who would dare to go against Him. The writer even seems to suggest that God will be imbued with a sense of loathing towards the Israelites which will accompany this punishment. Time and time again the impression, clearly given, is that God would cause these punishments to happen, just as he suggested that God would cause good things to happen(for the Israelites, that is) if they followed God's commandments. Either way the idea of God shown here is one who intervenes either in support of or against his chosen people.
There is no mention of either helping or not getting involved or things taking their natural course. On the contrary there is plenty about being involved, especially where vengeance and punishment are concerned.
As I said, I fail to see how the type of God depicted in this chapter has anything much to do with healthy parent/child relationships.