Firstly, OP, I want to thank you for such a detailed description of your life. I very often read posts from Nigerian society; for me, this is a revelation of how different people's lives can be in different countries. But I have a very respectful attitude towards all of you, because your country may not have all the charms that other, more developed countries have, but I see a great desire among people to improve the lives of their families. The attitude towards marriage is very surprising and worthy of an example for other countries.
I think you, OP, are very wise. I don't know your age, but everything you have planned looks very reasonable and mature. I say this because I have a comparison where it would seem that adults do not want to think about anything but entertainment; they have neither goals nor the desire to create a future for their children.
Your strategy and awareness will work for many people. In fact, it's hard to call it survival; I think you live a full, real life, and your children will receive many more good examples than even children who can study in private schools, but they have very few parents in their lives.
My respect.
I know it is some kind of utopia but I feel that the world should become much more solidaric than it already is. It is to a certain degree, but it could be even more. It is not only harsh conditions like OP described, and that is already harsh enough because nobody should be doomed to carry unnecessary burdens, but we also have situations of war or earthquakes in Turkey, sudden events that need instant help without any hesitation whatsoever and still there is bureaucracy stopping help from getting where it should have been yesterday in a best case scenario.
Nigeria is quite low in the list of income per capita. As OP described there are logistical inefficiencies like countless middlemen driving prices up etc. Why don't the wealthy nations set up programs that provide money and expertise to exactly improve the problems that keep those countries from prospering? I guess now the answer is that there is too much corruption involved and money from other countries like grants or loans seep away in corruption. But what is the conclusion? That our species is just too evil to be good? There are too many situations that prove otherwise, but still there are so many shortcomings and so much poverty in the world.
@OP in your case it's quite obvious that you are a smart mind, well-educated and ambitious to take things into your own hands together with your wife (what I said to you applies to her as well). But there are so many people in your country that can't dig themselves out of their hole like you.
I hope the best for you and I think your ability to sharply analyze your situation and adapt accordingly, especially investing time and effort into your children which I find particularly commendable in times of pressing scarcity, will pay off one day.
Let me finish with some pseudo-egoistic wish for you - I hope that your crypto holdings go to the moon soon, so my do, too!