How do i stop my wife from abusing my 7 month old son?

my wife is SO rough with my son that it literally is abuse, she jerk him around, jerks him up from the ground, ive wen to the bathroom to come back and see him playing with electrical wires. she has let him fall back on his head, yells at him to shut up, to STOP NOW, what he is doing, she will take away his bottle when he is still hungry for "punishment" and there is a lot more but i dont want to go into it, please someone, ive tried talking to her and she doesnt listen, she says she will do better but she never does, we moved in with her family because thats where she was most comfortable, so her mom just refuses to see it, and when she does its just "you shouldnt do that, or be careful" its like she doesnt care because she doesnt want to lose her "baby" i want my marriage to work, i love them both so much, i just want to help them, i just lost my job and have been looking for a month now, she constantly argues and yells, i want marriage counseling but she wants to pick the person, but ive tried to get her to call places and she hasnt, she lies and constantly denies things that she has done, and will lie to her mother about things i have done. i cant keep doing this, and i want my son to be safe, im 22 and she is 21, i dotn know if she was ready for a baby but i know she loves him, please someone help, i dont even know who i would talk to about this, and i dont know how to prove it, i dont want to make my wife look bad or abusive, i love her, but i cant keep letting this happen or im a bad parent. i dont usually take the time to record our conversations, or wake up at 3 AM with her to video tape what she is doing. and since im unemployed i dont know if somthing happened if our son would just be taken away. i would still want her to be able to see him, just under supervision, and when she got her anger under control then we could get back together, i just want everything to be ok.