TSG
Sounds like you have a problem with your wife, then the family. If a woman tells me to give up our son so we can "have fun" - I'm wondering what kind of person I married - lacking in compassion for your own child is not a good sign and bodes ill for the future.
Sounds like you're the money bag for this family and they're currently the money pit. As you're the bread winner - I suggest you take charge of your family - quite being polite and rule like a huangdi - my way or the highway, depending on who's house your living in.
Don't be afraid to call the police if the house or apartment is yours (owned) or a rental. You pay the bills - be utterly ruthless in tossing out your in-laws AND your wife if necessary. Don't know how old your son is - but assume he's still a toddler - however the home environment you've described does NOT set a good example to any child. He should be learning characters, poems, listening to stories, taking walks - keeping his mind active and eyes full of things. A live-in Ayi in Kunming will run anywhere from ¥800-2k depending on her experience. In Kunming I tend to pick younger ayi's (not for lascivious reasons) as they haven't learned all the tricks to stealing the home budget yet - but they pick up fast. Expect to trash an ayi every week until you find a keeper. Keeper means 3-6 months - unless you're extremely fortunate. Also - NO visitors to the home - your family (assuming you've kicked them out already) will try many tricks - try moving and not leaving a forwarding address if you have the funds - otherwise - be careful about kidnapping.
And don't take shit from anyone - if your "uncle" is derogatory - just tell him bluntly - the name he called you is offensive - he can either apologize or leave. If the family tries to interrupt - they can leave too - or you can leave with your son - call the police in case of ANY physical attempt to interfere with you - I doubt you're the seriously violent type so better to use the police.
Again - now that your son is involved - be ruthless in protecting him, nurturing him, and cultivating him. You're either IN the family or OUT of the family - there's no in-between. Be consistent, ruthless, and weigh your decisions carefully - and make no decisions in anger - be cold, calculating, meticulous - plan and execute - never look back.
A small problem at the beginning of your lives can turn into incredible ugliness, left unchecked. I know this sounds sexist - but that really has nothing to do with the situation - this is pure management of your personal life. Although we don't have your wife's side of the story, to be fair - playing majong all day (aka gambling, slacking off, lazy) is the equivalent of watching television (except majong keeps the mind a little sharper).
WIFE'S DIPLOMA
It's probably a 2-3 year degree - these are considered Junior College or Associate of Arts (AA) degrees in the USA. They are preliminary to accredited 4 year degrees (BA/BS). With a AA and the appropriate college entrance scores - one can usually graduate from a 4 year university in 2 years - this is a trick to significantly reduce the cost of a 4 year degree as Junior Colleges used to be a LOT cheaper than universities.
It's always heartbreaking to hear of any family headed towards a breakup - so hope whatever actions you take will create a sustainable harmonious environment for your son to grow with minimal emotional damage.
One last comment/warning - beware your son's genetic heritage - the things inherent in your wife's family may be passed to your son (laziness, gambling, selfishness) - you'll have to deal with these things and curb them - so plan ahead - control the situation and the environment. You KNOW he'll manifest these things so create situations and lessons to teach him responsibility, self-discipline, and balance selfishness with social responsibility.
Best wishes - feel free to PM me - I spent the last 5 years all over China as a single parent of TWO children and have seen more evil than good, both in China and abroad - but better here than elsewhere.
Experience comes from making both good AND bad decisions - I'm experienced - but what works for me is just my situation - your situation is obviously different - but you may find it amusing - and I see you are learning the art (dao) of being tao yuan (annoying). It is truly a marvelous skill - helps keep one sane in a world of extremely annoying pests.