@Dovegiven,
You said: “Where does scripture say "Satan in him" in that context?”
I don’t know how you read it but I read that “sin is Satan” (his kingdom), just as God told Cain, “sin” lies at the door and “his desire is toward you;” before Cain killed his brother Abel (Gen. 4:7). This is what Paul is saying. This is learned in meditating on God’s word. Yes, Satan is not in Paul, but his influence through harassing spirits of darkness tempting him.
Rom 7:20 Now if I do that I would not,” it is no more I that do it, but
“sin” that “dwells” in me.
”
Gen 4:7 If thou doest well, shall you not be accepted? and if you do not well, sin (Satan) lies at the door. And unto thee
shall be “his” desire, and thou shall rule over him.
You said: A recurring habit of a sin pattern is originated in the mind, the memory. A sinle event in our life can root in the memory such that we relive the event, adding to it by imagined furterence of the event, an escalating event brought to a hoped for present or future outcome. It's all a figment of the mind perhaps initiated and bolstered by devilish encouragement.
That’s not what scripture says:
Eph 6:12 For we wrestle not against flesh and blood, but
against principalities,
against powers,
against the rulers of the darkness of this world,
against spiritual wickedness in high places.
Eph 6:16 Above all, taking the shield of faith, wherewith
you shall be able to quench all the fiery darts of the wicked.
You make it seem like a man is fighting against himself; he’s not. I agree we must practice our speech in mediating casting down every high thing that exalts itself against the knowledge of God; but this is done because we are literally fighting against Satan’s kingdom. The only way we get God’s word in us and understand it is through meditation.