Counseling can show its effects a LOT sooner than you might think. Especially if you just focus on you two as a couple, not as a whole family.
If you two seek some counseling to strengthen your marriage, he may quickly become more supportive and empathetic. For many people, all it takes it having the outcomes of their behaviors explained to them and an "action plan" to behave better laid out for them...
He says he's willing to do anything to make it work, so I'd say that's your potential solution right there!

And maybe if the SKs see the threat of a breakup as real, they'll smarten up a bit and treat you with more respect. Would they go to family counseling with you and DH asked them to? There's no harm in asking if they're already a bunch of jerks to you both and you're about to split!

As for your two major problems...
1) I think he has a point - when you marry someone with kids, you marry a family. But he does need to understand how you feel and try to help you with it, so you also have a point. Please try counseling! It might help sooner that you think.

2) I think his plan of a second family home where everyone is equal might be a potential solution to the dynamics... I'm not a big supporter of this as Plan A, because I think the kids should treat you and DH with respect no matter what home you're all in, but it could be worth a shot now that you're at Plan B (or maybe Plan J or Q??). Get a family home, let the kids choose their own paint colours and decor for their own spaces. I know these kids have issues with even simple rules about human decency, but ask them to help you and DH make the rules for the house that EVERYONE will follow, set the consequences for rule-breaking as a group too. They may be less angry in a space they feel is their own (I know I was a happier late-teen once my dad finished building the walls for my bedroom and I didn't have to camp on the couch in my SM's living room and keep all my belongings in my car anymore).

Would you be willing to try the family home + counseling for six months to see if the outlook is brighter?

Thanks for the input.

At this point, I am not sure how much energy I can put into my marriage. I feel pretty burnt out by the situation.

Since we were having problems adjusting, I thought the best idea was to get a family home near where the SKIDs live, so that they can spend time with their friends and have their father seen in the community. Then, if they want to come to the homes I had before we married, they must follow rules of common courtesy. Right now, they treat me like dirt in my own home, which has to do with DH's inability to set limits.

Getting a neutral territory takes me out of being a gatekeeper between them and their father. It also empowers me to be able to set boundaries and limits in my own home, something that never seemed to happen in their parents' home. (Recall that SS told his mother "The only thing you care about is getting yout p*ssy f*cked.)

DH raised the topic of getting a new family home together with me in the town in which they live, but SKIDs didn't like it. They want to come to my place in the city so they can go out and party. The saddest part is that it has nothing to do with seeing their father but rather their desire to be entertained.

The tension isn't about me not wanting them to spend time with their father. (I told him that he could spend every weekend with them, and I would be fine with that.) They want to dictate where they are willing to see their father, and they want to use my city apartment as a launching pad for fun weekends with their friends.

Frankly, I feel pretty exploited. So I am not sure what to do. It is hard to be mistreated in your own home.

Isn't financially draining to keep that many houses and apartments for the sake of seeing kids? Isn't it kind of pricey? Keep a neutral place costs so much! I wonder why do you have to spend that much money on a separate place? Kids shouldn't dictate what house or what area they will be seeing their father. It is not up to them.

On the other hand I would not judge that phrase about "P. being f." that hard. Kids say it when they are denied attention and when mom makes her personal life a priority. It was said because of the pain they experience. I really would not judge them for what they say to their mom.

Well, we are lucky to have the money to support multiple households. But as someone here aptly pointed out, it is a logistical solution to a problem in the marriage.

I don't think the SKIDs ever resolved their feelings about their parent's divorce. So I am an easy target for their frustrations. (I think that is fairly normal is a stepfamily.) The key is to have DH defend his wife. Without that, I think the second marriage fails. Because the SKIDs know that they are free to misbehave.

I also think that the SKIDs know very little about boundaries and limits. Again, it isn't their fault, it was how they were raised.

Can I see myself as a family with them? Not really. DH has the one big happy (or unhappy in this case) family. So we really have a situation that I think is impossible to resolve.

firedreams...I disagree. With a child who speaks like that to their mother or father...where do you even begin, to change such family dynamics??? I would imagine that it will be a long and hard road ahead to change family dynamics that have hit such a low point.