@SirChing, your post could have been written by me - pretty much word for word - 20 years ago, concerning my father's mother's funeral. When she died, she was essentially being used by her youngest son and his children as a housekeeper; yet not appreciated in the slightest (think, spending all day preparing a hot evening meal for the family in winter, then being summarily dismissed at 6pm so that they could "eat as a family", and having only sandwich ingredients in her cold home because her gas oven leaked if used and youngest son refused to help her source a replacement/allow her to have it repaired "because of the cost"). The last time I spoke to my grandmother, she actually cried - and I'd never heard/known her to cry before, she was such a strong, resilient person - about how she was being treated, and I started to make noise about her coming back down south to live with my small daughter and me. I was furious about the way she was being treated, and told my father, expecting him to... I don't know... get the youngest or middle brother to do something to help their mother. He didn't. But he obviously told them how furious I was, or my grandmother mentioned that she had an offer of a decent home 400 miles away with me because, two weeks later, when she died (very suddenly; heart attack), and her funeral was planned? My father told me that I wasn't allowed to go, that one of the children of the youngest son had threatened to kill me and my daughter if we turned up (he was 16 at the time, a nasty, arrogant piece of shite), and both of my uncles (my father was the oldest) agreed with him. Both of my parents went, they all pretended to be one big happy family, and my daughter (who was 3 at the time) and I said "goodbye" in our own way.
I have never regretted not going to the funeral, because I knew that my grandmother would have understood, had she still been alive. I suspect yours would, too, SirChing. There were a lot of people who didn't understand, however, so I used the excuse that my grandmother would have hated my 3 year old going through the funeral - which was true, as it happens. But ultimately, despite my younger cousin's ludicrous threats (he would have been told to keep his distance, by his father, who would have been terrified I would have told everyone that he'd sexually abused me when I was 7 and said son was a small baby! This is why I was NC with him in the first place... the middle uncle was equally toxic, but for different reasons - he refused to acknowledge the mere existence of my daughter, because I wasn't with the father when she was born, so therefore not married!), I didn't go because I couldn't see the point. Funerals are for the ones left behind, and knowing that my father had to have reported back my fury at the degradation they had heaped onto my grandmother's elderly shoulders, I refused to go "to support" him. He had my mother for that. My grandmother was gone; not there anymore/at peace. I'm still furious about the way she was treated, and cross that she didn't tell me sooner, but staying away was absolutely the right thing for us to do.
Maybe, SirChing, staying away will also be the right thing for you to do, too - but only if you know you absolutely won't regret doing so. For me, it was an easy choice. For you, it might not be. You will have to weigh the choices you have up and decide which is best for you.
I am truly sorry for your loss.