Cunning uncle with diffrent intentions

Hi, I just joined the site now after reading a few stories, and I wanted to add mine.
There is always this negative feeling I have that I didn't step up for myself when I should have. This all took place when I went for a vacation to visit family abroad.
Whilst I was still in the US my grandparents came to visit from the abroad country (not mentioning for various reasons), and once we left to go on vacation there was an argument between my aunties husband and my grandpa in the US. At this point we didn't know anything about this.
It was until after my grand parents came back did we know that there is a big issue that needs resolving and our family was bang in the middle of my aunties family and my grand parents (moms side). Which still hasn't been resolved
I have this uncle who was on a mission to get me hitched to his daughter (my cousin). He did countless things that made me feel as if he actually cared about me e.g. nice trips out and just generally having fun. The problem I have with his efforts are that these were hidden intentions behind all the fun and games that I didn't know about until after a huge argument between the families.
It was at this point that my dad told me his intentions and I felt as if I had been used. It just so happens that I found a partner whilst I was there. So me and my parents decided to approach the other family and they agreed to get us engaged.
The crazy uncle mentioned above is my grand parents son and my mums brother, so he got chatting to them and filled them in that I am probably getting engaged with this other women before I leave.
So because of this they played "family politics" with us to break this engagement. Initially as a form of respect due to the blessing of the elders we thought it was best to seek the blessing of my grand parents and take them with us for the engagement but they declined.
I also should include that there was an argument which was part of the "family politics" used against us. When my fiancés grandfather who was a friend of my grandpa's, went to visit him after he had chest pains thought to be signs of a heart attack. But nothing major, anyways my grand father insulted him for no apparent reason and told him to get lost and etc in a bid to prevent the engagement as they could see it was coming as I am studying and I would go back to get married and so the engagement is best atm.
So before the day of the engagement my mum and myself went to tell my grand parents that these are our intentions and talk about it in the open, at which point my uncle was away. So they knew then that this would happen tomorrow. At that night my crazy uncle decided to play another game so he couldn't be blamed for what was forthcoming as he went to another town because of religious duties.
In the morning as we went to seek the blessings and ask my grand parents to come to the engagement and be a part of it. They started swearing at my mum and they wished she was dead because we are now going to form a relationship with their enemy. After which they told her to sit and not leave the house, meaning she had to break her marriage and to have nothing to do with my dad or us. At which point me and my father told her to get up and come with us to leave their house. As we were leaving, my grandfather went into the room next door and pulled out his shotgun in a bid to kill my mum.
So we stopped him and sent him in a room before we left their house. After this we got engaged and no one went to their house until the day of our departure. Before the engagement my uncle kept calling my dad in a bid to delay the engagement as it was a big event in our culture.
When my uncle came back he didn't talk to me once, clearly showing he didn't give a toss. When he came back he accused my fiancé of being 2 faced, loose morals etc. Then as we were leaving we thought it is best to meet everyone before we leave the country. So as we went to my grand parents house they again cussed and cursed us as we left.
In the mean time as we came back home we found out that my aunties husband prevents her from visiting us. Because of another issue to do with my dads sister-in-law also living in the same house as us (abroad) Otherwise he would divorce her, because of this she hasn't met us once since we came back.
My question 
As it is something that I would every relative to be there for, no matter how evil they are.
Thank you for your patience and also reading this and on the help !!!
PS any tips to counter such behaviour next time would be great and any insight on if we did the right thing or anything that we could have done here.