OP, you sound like a superwoman with Trojan strength and powers!
If you have managed 4 kids, all that study and professional development , a job, care for parents and running a household with no teamwork or partnership - you can do ANYTHING!
This is your strength going forward.
It is interesting that your Dc has noticed and comments on his detachment from family. and good that they question this. But for the younger ones - does it model a good healthy relationship?
You say he is generous, but you don't actually know that - what he transfers could be a tiny amount of his income.
He could actually have a parallel family elsewhere. This happened to 2 of my friends.
Whatever is going on, his treatment of you and the family makes me really angry. How DARE he let you be enough of a partner that you care for his parents but not even tell you about insurance for the house you live in? Or your joint family income? He doesn't deign to give you the information to know for yourself whether your family is protected (life insurance), your home at risk etc.
I hope you are on the house Deeds? Are you on the mortgage?
Gather your IMMENSE strength, gather your info.
Is he registered as the director of his company? Check him out on Companies House and look at the accounts.
Check your house on the Land Registry - make sure he has not put a charge on it for re-mortgaging and that your name is there as a co-owner.
Work out how much equity there is on the house. If you are on the mortgage you can approach the company directly - get statements sent direct to you.
Scour the internet for his name, company name, people he works with - see how much they are charging, scale of jobs.
Talk to a solicitor about how much you would be eligible for in a divorce - tricky because obviously he will be highly secretive about his savings, pension, value of his business etc.
The leave him,. He is a total bastard. IMO.
But you - you are strong, resourceful and of generous spirit.