D.K.
What your husband is not only destructive to your marriage but to your daughter as well. Allowing her to hide a bad grade and not have consequences, to have her feel it is you against the two of them is wrong on so many levels.
Parenting together requires very consistent, clear and united rules. If there is disruption, hiding things, mistrust and bullying behavior then you all are doomed to fail. Your daughter is not learning anything by what her father is doing!!! Nothing other then to disrespect you! You seem to have other issues with your daughter, which I too remember those bumps with my mom. Try to find resources, the school counselor even or good books to help you feel better about how you are doing things. I don't think your consequences were bad at all! I think the problem is your husband.
I would sit your husband down, hand him the book "What Fathers Do Best" a great book, then tell him that he is causing problems, big ones. He is your husband and though he may disagree with your consequences, he must back them up when you lay them down and vice versa. You all need to get on the same page as discipline and consequences and stick with it (btw I agree, bad grades no cellphone!!). Kids that feel entitled will carry that on and it can be such a disaster for them in the real world. Does he think he is doing a good thing for his daughter?
Being a parent alone is hard enough, but in order to do it together you have to be the united front. Leading kids down the path of pubertiy, peer pressure and all the chaos that goes with teenage years, if you two don't stand united you could be setting yourself up for drug use, promescuity and dangerous behaviors. It is a time of testing boundaries all over again and you have to give her clear rules and consequences if those are broken. It is helping her, not being mean!
All your husband is doing is teaching your daughter that lying is okay, that there are no consequences in life and he will regret it. Remind him he has ONE shot to do things as best as he can right now, in 3 years she will be on her own, so he better think before he does this stuff!! If he loves her, he will change his tune!
YOU have every right to be upset and I suggest counselling or therapy soon!