I agree with the other posts that you have a parenting issue. You and your husband don't know how to talk to each other. You have a history of being taken advantage of by your own daughter, according to you, and he helped you recognize it. However, if you talk to him about the same thing, he can't handle it and he "jumps all over her" (as he did with you) but then apologizes - so he is inconsistent with her and hypocritical with you. You and he side only with your own children and have no relationship with each other to be able to have a civil discussion (without "jumping all over" and getting "infuriated"), and you are unable to establish and maintain house rules for your part-time guest (your daughter), your full time family member (his daughter) and your full time boarder (the boyfriend).
Your daughter is 17 and stays with you "every so often" so she either is emancipated and has her own place, or she lives with someone else (perhaps her father)? So she has another place to live most of the time. If she still has her own designated room in your house, put a lock on it. You keep one key (for safety only) and she keeps the other, and she's in charge of her own laundry.
Your stepdaughter is 18 and lives with her boyfriend in your house. Put a lock on their door, and her father keeps a key (for safety only) and she keeps one (make a third for the boyfriend). They do their own laundry which is not mixed with other family laundry. A closed/locked door will hide the clutter - why do you care whether she cleans her room or not, if you don't have to look at it?
So you have 17 and 18 year olds who cannot talk to each other, and who run to Mom/Dad when there's a problem, and the parents capitulate. You have an 18 year old who doesn't work and who lives off Daddy and you.
I don't know why this situation would be anything but where it is - off the rails and in the ditch.
You either move them all out, or you have house rules and charge rent and stop cleaning/cooking/food shopping/laundering for anyone over the age of 13. Period.
If you cannot do that together, then get into marriage counseling immediately. You and he aren't setting a good example for conflict resolution, and so it's obvious that the kids haven't learned anything either.