Your family is very dysfunctional and sick, Pof5.
I don't think there's one person in particular who is unhealthy-- the whole dynamic is unhealthy.
You were avoiding being home by going out and drinking. I can understand why your spouse had a problem with this. And you chose to put yourself in a bad position when you didn't come home at night. Try to remember-- as stressed out as you are, your kids need to see you coming home at night. When we don't return all night, this is significant, and I think you know this.
It probably would have been better if you and your husband had stayed separated if there's so much tension that you are always arguing.
That said, your mom and sister could be worried about you,but they aren't showing this in a healthy way at all. And your mom waaaaaay overstepped boundaries by going in to your work. You need to tell her to NEVER, EVER do that again. That even if you completely and royally mess up, she needs to only help you in IF and WHEN you ask her for help.
Are you going to any sort of counseling, talking to anyone about trying to repair your marriage or make boundaries with your family? I don't want to stretch things too far, but my guess is that these issues are compounding your depression and negative feelings about yourself.
Figure out healthy ways to deal with the tension in your marriage. Maybe the separation needs to happen, maybe you need more help with a counselor, because marriages rarely just heal themselves. But I would work on becoming a team with husband when it comes to communicating with your family. I mean, your husband DID unload and let them hear about his every complaint he has about your behavior-- so some responsibility needs to go there, but your mom's reaction of going to your employer was beyond the pale. I'd work on making some very strong boundaries with your family.
For what it's worth, when I was processing my relationship with my ex, (while we were still married) I had my eyes opened to the massive amount of dysfunction that was going on in my own maternal family/my mom and why/how that DID carry over into my other relationships. I know your plate is full right now, but this is worth examining. Usually, how we are treated in our first family home sets us up for choosing the partner we have and how we function in our own family with our kids and spouse. ***You want to identify this stuff so you don't pass it on to your own kids.*** Try to go forward being more solution-oriented and do get some outside help as you work on this stuff... it's hard to go it alone, and if you don't have support from your family and support is only conditional from your husband--well, you NEED support to make good changes. Said as someone who has 'been there, done that', felt lower than low and has walked through fire-- change is hard, but it can happen. Good luck.