OP, you sound like a total nightmare.
I can see that you're manipulating events which can have massively different interpretations into a "it's not fair, it's not my fault" viewpoint, but look at the examples you gave:
Arranging free furniture might be a wonderful, welcome new gift vs another attempt at controlling what your DS and his wife decorate with, with something as personal as furniture
Your DH telling DS about all the health issues caused by the stress of it all meaning he knows how seriously it's affected you vs emotional guilt trip designed to make DS pick you over his wife
His DB and SIL trying to reconcile the family during a normal visit vs pressuring them and interfering in a situation which makes your DS seem unreasonable
The misunderstanding about the wedding plans and making you feel like "guests" might simply be that they haven't acknowledged the blended culture of the marriage sufficiently vs you had completely unrealistic expectations about the norm in their culture and expected it to revolve around you
the 40 people turning up could be a simple misunderstanding (see culture above) vs your attempt to lash out at your DS on what should have been a happy occasion, blaming him for something that he had no control or foresight of.. just what did you think you'd achieve by punishing him?!
.. and so on.
All these little events, and the way they're worded, remind me of some of the really toxic parent, PIL threads on the Relationship forum of Mumsnet.
If you're expecting posters to say "there there, you're great parents, selfless, caring, poor you" - well, that's not the sense I'm getting from your post at all. You describe highly ambiguous situations and events, and seem to make all of it about you, your needs, your expectations, and there's almost nothing in there about actually communicating with your DS on what he thinks the problem is in the relationship. He's clearly decided (due to "all the arguments?") that it's a nicer life without you in it.
You each have your subjective viewpoints on whether that's reasonable, but you shouldn't be looking to AIBU posters for reassurance.. you should be trying to figure out how the relationship got so broken, and truly listen to your DS to find out how it might be rebuilt.