No you have not taken what scripture says about it.
Like many Christians, you have just used some scriptures to extrapolated a false theology for your preferred narrative.
That's understandable because that narrative means that you can now comfortably avoid the direct commandments of Jesus to cast demons out.
Here's your problem.
I'm sure you have read that Jesus issued the commandment to cast demons out as a part of spreading the gospel.
Those demons have two possible types of host body, unbelievers or believers, and you have rejected the latter as a possibility.
If you are indeed correct that believers can't have demons, then you are obviously obliged to drive them out of non believers.
So how well has your casting demons out of these unbelievers been doing then, or have you avoided that also?
You also have an additional problem with unbelievers having demons, and that is, being unbelievers they don't believe in demons or any other of that daft spiritual stuff, and certainly won't let you lay hands on them for deliverance!
And as for your idea that demons can't inhabit a place while the Holy Spirit is there, go read about the OT temple. You will see that it was full of evil spirits while the Holy Spirit was still there.
As I said before, I have been casting demons out of the saints for 40 years, and have seen their lives radically changed.