Stuck in the middle of parents divorce.

Hi I'm looking for some advice and support, Sorry if it's long but I don't have any friends of anyone to talk to. I've always had a bad relationship with my father and hated him most of my life, he walked out on my mom and me last year, it split my family apart and he did it in the most horrible way, my mom still won't speak to him (there's a lot gone on in the past and it wasn't a happy marriage for my mom, he was an alcoholic and abused her emotionally and mentally). I've been stuck in the middle ever since, I finally managed to get them to speak to each other with me there and they agreed that me and my mom could keep our house if she divorced him, this was 6 months ago and my moms filled out paperwork but I feel like now she's trying to drag it all out to spite him, I'm worried he's going to change his mind and try to take our home if she doesn't get the divorce sorted out. Everytime I speak to my father he asks when my mom is going to the lawyer to sign the papers and I keep lying to him telling him 'there was a problem she's going next week' I think he knows I'm lying but I can't tell him she's not going yet or he'll get annoyed and be spiteful to us, when I ask my mom when she's going she gets angry (someone in our family died recently and we've had a lot of bad luck since he's left, it's not been easy) I feel like she's using the death as an excuse but I don't know how talk to her about it without us arguing. How do I get her to see its killing me being stuck in the middle? I just want her to sign the papers and it all to be over and know my home is safe. Thanks for reading any advice appreciated.