Stacey is a witness to say that the person who hit Max did it diliberately. They aimed straight for him and went faster until the moment of impact. If Jack can get Stacey to change her story or revoke it then Tanya could merely say that she didnt mean to do it and tried swerving away from him but still hit him accidently. If you get me.

I still think Tanya is covering for Lauren. Yes by doing so she is losing her 3 kids but no matter what she is still protecting her daughter. Tanya is probably feeling guilty as well because even though it was Max that did everything wrong in the past she will always deep down blame herself for letting him do it and letting the kids see.

Plus i think that Tanya thought that she was going to get bail and then say it was an accident but now Stacey has become a witness it seems less likely that will happen.

In my honest opinion i think that Max deep down knows that Tanya didnt do it and helps to prove her innosence. Maybe that way he will discover that it was his daughter who tried to kill him and then he will realise the extent he has drove his family to. After all if he didnt do what he did in the past none of this would have happened and in a sort of way it is all his fault.