Even though they are way to old for it.. Make a rule sheet. List what they are supposed to do every day. List the house rules. That way they can not say " I didn't know"

Ohhhh NO!!! I had the same issue when DH and I first started living together, married. I also work from home. DH and BM thought because I worked from home that I could be the "nanny" and keep the kids all summer and every day after school. Of course they used the whole "its your duty as the SM" crap and the "Don't you love my kids?" guilt trip. My SS's would also refuse to follow any rules, steal from my BS, leave trash everywhere, fight, scream, yell, tear up the house and generally be horrible. And they were all old enough to know better....Early teens and preteens at the time.

I would try to correct them but I was also trying to work. It's not like I could sit in the same room and babysit every second. Then BM would pull in the drive, honk and they would run out the door leaving a huge mess, the door open and every light in the house on.

I finally told DH that I was at my limit, they needed to either stop the messes, and screaming or I would not be watching them any longer. They didn't stop. On top of that, BM was showing up later and later everyday to pick them up and not giving me any warning she would be late. She actually made ME late to meet my XH to drop off BS for his visits.
I politely text her (because she never came to the door) and asked that she give me a warning if she was going to be late as I had other places to be. She unloaded on me telling me how much I hate her kids, blah blah blah.
Finally I had enough and gave DH and BM a week to find other arrangements. I was done.

I honestly believe and have told DH that by forcing me to watch the SS's (After I had said I wouldn't before we even moved in together) they actually ruined my relationship with the SS's. I became the heavy from day one and our relationship has never recovered. I am not close to my SS's at all. I rarely see the oldest two and it has even affected their relationship with DH. If he would have listened to me, our time with the SS's from the beginning would have been much more peaceful and enjoyable. DH and BM pushed them onto me to avoid parenting and now we have a fractured relationship with the SS's.

I would tell your DH he is ruining the family dynamic and he needs to either find other arrangements or you will find somewhere else to work during the day.

Disconnect the wifi
Lock up the junk food
Shut the electricity off

And it stays that way until the house is cleaned from their mess.

My stepchildren are 16/10 and know not to act like heathens because
this SM has no issue laying down the law.

Especially for the SD16 who's only here 4-6nights a year
because they know I have no issue tossing their shit out the door
or sending them back to their mother

or set up webcams to show your husband his lovely girls

You tell your DH and the SD15 that if she and her sister can not behave as young ladies, DH will have to get a sitter for them as you will no longer be their baby sitter.
When SD whines she is too old for a sitter, you point out that No, you act like a child so you will be treated like one.

You may need to make other arrangements to work somewhere else during the days they are at your house and then you leave on those days and let your DH figure out his children care.

Edited to add: I just read you dont want SD alone in the house. You can put a dead bolt on your bedroom door, and your BS, and look stuff up in the bedrooms.

You have 2 choices: Stay and be miserable or force your DHs hand. It isn't going to change by complaining, I've found men don't respond to nagging, they respond to action.

Tell DH: "The minute you walk out the door, all the rules we've made go out the window. SDs' do not respect me or you and they flaunt that as soon as you leave. Since you refuse to believe me, I am installing NannyCams/Survelliance/will be recording with my phone/etc. I expect you to watch the footage and then start backing me up when I start handing out consequences."

If the girls behave when DH is home, they know what the rules are. They just don't respect you or think that DH is a total idiot who will never catch them. DH will need to enforce to the girls that you are his voice when he isn't home and he will back you up. Since they have been getting away with it for 6 years, its not likely to be a smooth transition but it can happen if DH is willing to step up. A real hard-ass dad expects his kids to respect his rules in his home, even if he isn't there.

The worst part is I'm becoming the problem. I can see it in DH's face every time I try to talk to him about the goings on of the house.

^^^^^ This and your post is exactly what happened with me, DH and girl skids. If you and DH do not get on the same page it's only going to get worse. SDs are only going to get worse as well. I

When my SD was old enough for a job, she applied for a few and didn't get callbacks, So I told her we would go into every business in a certain area and ask and fill out applications...we did, and she got her first job (at a dollar store). While it wasn't a great job, it was a great learning experience and she got a better job the next year as she had experience! My son was out shopping with me and wanting his first job a few years later and I told him the same thing, we were in a strip mall with a movie theatre, restaurants, grocery store, etc. He went in an applied while I was shopping and got hired on the spot at the five guys and has been a good employee and learned a lot.

First jobs are hard for kids to get on their own if they are at all shy or lack confidence but it can be an awesome game changer in their personalities when they have their own money to spend, own bank account, etc.

Also the 12 year old is old enough to help neighbors with weeding, pet walking or babysitting (a mother's helper) if you live in a development.

PS. stop the handouts and don't give up on them, you could be the best thing that ever happened to them.