I’m so scared

We are going to be welcoming our second baby in December. I am so scared because our 2.5 year old is such a trying person. I love her more than words but she is extremely jealous and very demanding of all of our time. If we ever try and do anything that isn’t dedicating 100% of our attention to her she will scream and hit and throw things. I don’t believe in spanking. I grew up in an extremely abusive house hold. My mom hospitalized me at 6 and when I lived with my dad he would chase me and grab me by my throat so I have a problem putting my hands on other people. Time outs don’t work, taking toys don’t work, ignoring the behavior doesn’t work. My husbands mother watches her during the day which I am thankful for but she doesn’t set rule or boundaries. She isn’t ever made to entertain her self or be happy with the green cup because that’s what you got today. So then when she sends her home we get to deal with a child who has a my way or no way attitude. Which I know terrible twos but my child will hit and bite and scream in your face. I’m about at my wits end and don’t know what to do. Any tips would be great! I know everyone probably thinks I’m a shit mom and I know a lot of y’all will have no issue telling me that but rest assured I already know I am and feel like a horrible mother.