Where in Scripture is homosexual orientation attributed to sinful acts of human beings?
As a matter of fact it takes a careful and fairly selective reading of Paul to get lesbianism into the bible at all.
Romans 1:26
For this cause God gave them up unto vile affections: for even their women did change the natural use into that which is against nature:
Anal intercourse is "against nature" for men. Women could have allowed anal intercourse, not practiced lesbianism.
Incorrect.
While admittedly the language is rather convoluted by modern standards, it is not incomprehensible. There is no textual support for your claim that Paul is speaking of isolated acts as opposed to general rule.
If by use of the term "orientation" you mean to incorporate the modern understanding into the Pauline discourse, you should understand the two are mutually exclusive and can not be reconciled.