Also, the grace of Christ is the fulfillment of the law in both letter and spirit. Was not Christ’s sacrifice on the cross sufficient?
You will indeed find your verses calling for the killing of homosexuals in Hebrew law. But why are you not arguing equally vigorously for all other provisions of Hebrew law to apply in civil government? The verses about being worthy of death apply to many sins you sin too... are you going to commit suicide to oblige them? (I think not.)
The trouble with your theory is that when taken to its logical end, it simply fails. A theory of grace, however, succeeds and succeeds wonderfully. Grace is not indulgence.
Rawr, rawr, rawr goes that roaring lion, trying to use the power of the law under the revelation of grace, not realizing it is a weapon that blows up lethally in his hand.