Had a similar discussion with my fiance about SD7. 

She kept telling little lies and directly disobeying simple commands. I sat my partner down and explained that this kind of behaviour wasn't okay and if we had children I would be going crazy if they did that. 

He eventually caught on that I wasn't messing around and being serious and he has started to move to listen when I'm asking her to do something in case she ignores it. 

It's taken nearly a year but we've eventually got there (I think) 

He understands it, and he knows that it's not unreasonable to ask a 10-year-old to pick up his room, he's just afraid that if he's an actual parent to his son, his son won't want to come over anymore.  If you take over as the New Sheriff in Town, the son probably won't want to come over either. So if BM is the type to withhold SS, or allow him to refuse visitation because there are rules in your house, either one of you setting limits will cause problems.

I'm not saying that's a reason to allow SS to be feral, but that's probably what your husband fears. Instead of saying that, he tries to make it seem as if you are just unreasonable.  So do you push the rules and stoke your husband's fears, possibly causing SS to refuse to visit; or do you just let it go, close the kid's door and let DH be the parent - that's up to you.

You have two different things going on here.. "how do you get them to see their child isn't perfect" and "The child doesn't have any responsibilities and isn't taught to clean up after themselves."

Children can only be expected to do or behave as they have been taught.. it's not the kid's fault that their parents have not taught them to do things. YOu think that a child that age should be capable.. but that really only applies if that child has been brought up with slowly increasing levels of expectations.. it would be like me expecting you to speak fluent russian when you have never gone over the basics of that language and had years of increasing learning.

So.. the other issue is does your husband want what is best for his child.  Obviuosly, it's important for parents to teach their kids life skills.. like making a bed.. running a vacuum cleaner.. tidying up.. because they will need to do this for themselves as adults.  

There is also the  matter of hygiene and cleanliness.. if the room is fetid with dirty laundry and food dishes/remnants.. that is a health issue.  And... while you can close the door on a messy room.. one that is rotten is a different matter.

Maybe you and your husband need to have a small talk about why it frustrates you that he doesn't seem to be teaching his child like you were raised.  That you think it is hurting the child to not learn to be more responsible.  You aren't expecting the kid to scrub the bathroom with a toothbrush.. but making their bed every morning and putting laundry in the hamper and clean clothes back in their own drawers.. putting a toy away when they are done.. those are simple expectations and you don't understand why he objects to the thought of his kid performing any of those tasks... no different than expecting he will wipe his own hiney and brush his teeth twice a day.

It may be that as a NCP he feels he doesn't want to "fight" his kid while he is visiting.. but certainly, he can be doing these things in cooperation with his kid.. for a while he may need dad to help him.. show him and participate in the habits.. then he may become more self sufficient.  In the AM.. "Ok buddy... let's make that bed up.. and help him do it".  When laundry is done.. bring the pile in and hand things to the boy and direct him to hang up.. or put in drawers.. helping along the way.  etc.. 

Have you asked him if his son will still be cute when he is incapable of making his bed when he is 20? What about not knowing how to load a dishwasher before he leaves for college? How well do you think his dorm roommate will take to a nasty slob? What about a nice young woman one day?

We have to teach our kids these things while they are young. We teach and we have expectations of our kids. Then once they are 18(ish) we release them into the real world and hope that we have given them the skills they need to be productive members of society. So they can marry and have their own family one day and make us grandparents. That they will be self sufficient and we can move to the friendship stage of parenting. 

However, if we don't act like responsible parents and teach them these skills now, all we will have is a failure to launch kid living in our basement forever. That is NOT ok. 

I have SS9 going on 10 this month. My DH his feral child is a prince too. At this point, I stopped doing it. I stopped talking to the child and completely disengaged. But, when I want something done I do ask SS to clean his room and I let him know if he doesn't do it I'll take his play station away. I don't care if he tells his father. This is my house he is to respect it. It is not unfair to want or expect a 10 year old to do the simplest and yet most common task in their life! You aren't asking the child to clean the whole house. It's simple shit and DH doesn't want to parent his kid. He will allow this child to do whatever to please him. I would have a conversation with him. He is scared he will actually have to act like a dad and put a little vase in his voice to get his kid to do something simple.