In laws 😒 rant

I have an absolutely fantastic mother in law but no so much her mother (hubbys grandmother). She lives right above me in the same apartment building. Walks into my place whenever she feels like it, hands my son (2 years old) junk crap food before supper like cookies, candies and chips, trash talks me to her whole family, calls me a bad parent, treats my hubby like hes a child (no joke she still buys him superhero underwear) and the most annoying is telling me how i have to spend my money and what i can and cannot buy. Yesterday she informed me she is taking me to an expensive mens clothing store so she can help me pick out my husbands work clothes. When i informed her i was taking him to walmart instead (clothing to ruin in labour intensive job) because its going to get ruined and i cant afford expensive with second child on the way, she flew off the handle screaming in her works parking lot saying her grandson deserves better than me and that i need to start taking care of him. (my jaw dropped and i couldnt even attempt to say anything back). We come home later that afternoon and hes on my side about apologizing on her behalf and now today hes pissed off at me saying i need to respect elderly people and that i was being rude to her. Come to find out she called him after i went to bed spewing bullcrap saying i was yelling at her. I told my hubby we are moving because i cant handle her and he suggested i take our son and unborn to a new place and he will move in with her for a while so he can stay close to her. I am so upset that something so stupid could ruin our relationship but im not sure what to do. Any suggestions? I feel like iv failed my children