However, that's only the "LUST" issue. there's NO SIN until you allow the LUST to "Conceive", and give birth to Adulterous ACTIONS.
Well yes as the topic was adultery in Matthew but as I pointed out in James, sin is born out of our desires that ignore God's word. Whether the motivation is lust, greed, pride, jealousy, etc. makes no difference, it will result in sin in all it's various forms.
Nope, the "Serpent" (the enticement) is still external, and there's NOTHING CORRUPT about our "DNA". Jesus (with the SAME HUMAN NATURE WE HAVE) was Tempted IN EVERY RESPECT AS WE ARE, but never allowed HIS LUST to "Conceive".
Our DNA is corrupted because as Romans 7 puts it there is
another law at work in our flesh, a law not put there by God. It is why we get sick or are born with deformities/abnormalities and ultimately die. Jesus had the same human nature because our "nature" (ie. that which makes us human) is to be found in our soul not our body, yet He was with out sin. This is a reference to the sin nature found in our flesh not simply that He never committed any sin (He didn't commit any sins either just so we are clear on that). This sin nature is passed on down through Adam ie. the male line. It is why Jesus had no human father.
Jesus never lusted after anything. I think you are confusing desire with lust. Desire, in and of itself is not wrong. Indeed, God promises to give us the desires of our hearts if we delight in Him. Desire is not corrupted until it draws us away from God's truth. Christ was never drawn away from the truth, indeed he is the truth.
Psalm 37:4
Delight yourself also in the Lord, And He shall give you the desires of your heart.
Our flesh does act like a serpent in the garden which, is not to say
all temptation comes from within. It is said to be against the Spirit (Gal.5:17) because the flesh doesn't think, it simply reacts to circumstance/environment and seeks to preserve itself in that reaction. This is the temptation and so, without God's truth to guide us and the power of the Spirit (grace) to overcome, we are led into self-preservation, self-indulgence, self-serving thoughts which lead to sinful actions.