I agree about the secrets. Here's the situation you want to be dealing with:
He has a cordial relationship with his ex and they agree on a shared parenting plan. He takes his responsibility to his son seriously and nurtures the relationship with his son and family.
His family is interested in meeting you and welcomes you to their home b/c he has said such great things about you. They do not make you feel insecure b/c of issues of caste.
As a 35 yo adult, the fact he can't facilitate any of that says to me he is still essentially a child. Is this really the kind of guy you want to be father to *your* children? Sounds like he needs a mom. This is the reality of what you will have to deal with if you marry him. Once the romance bloom fades, you are going to be the one worrying about these things. Just like you are now, here on this forum.
I suggest you tell him what you want, what you think is reasonable for your situation. Tell him to call you when he's got his life and issues sorted out.
Second thoughts can generally be amended with judicious action; injudicious actions can seldom be recovered with second thoughts.
--Cyteen by C.J.Cherryh