Re: The guy and his family coming over
Do you see the contradictions in your own statements? If you don’t want to do anything stupid and don’t want to get attached without knowing for sure that the guy AND his family will say “yes”, then why did you already fall in love? You already are at a point where you can’t stop thinking about him. 
Just act normal. The families have known each other for years and you have met/talked to this buy before. No reason for you to act like this is the first time you’ve met him. Stay relaxed. Act like this is a family that your family has know for years and they’re just coming over for a visit.
Based on what you wrote, it sounds like you need to talk to the guy more and find out if you’re truly compatible. Do both of you want the same things in the future? If you marry him, I assume you’re ok with moving to Silicon Valley? What expectations does he have for his future wife and can you fulfill those expectations?
Also, don’t you have a child that’s 9/10 years old? Please correct me if I’m wrong and am mixing you up with another poster. But if you do have a child, then you would obviously need to make sure the guy is willing to accept the child without any reservations. If if you do indeed have a child that’s 9/10 years old, are you planning on introducing your child to this guy at all before finalizing a decision?
Having a common language/culture certainly helps but if you have not yet discussed anything specific with this guy in terms of marriage, expectations etc…then you have no clue whether he’s compatible or not. By allowing yourself to get attached so quickly, you’re only setting yourself up for stress and potential heartbreak.