Not That I know of, specially if they were out bred somewhere along their line.
As far as I know scaling over the eyes occurs by chance if both parents have very thick dragon scales. If you want to eliminate this possibility simply breed The thick drgn scales to a non dragon.
I've been breeding drg-drg but haven't had any drgn scale on eye.
Always set a goal before you breed, even though just for mere experience (that's a goal too). That way you'd know what to look out for and later, whether you succeeded or not ..... in the long run it will give you better insight. And for me, I know how to guide you in a better way.
Yes. If both are extended red (including the marble) you should have ext red, red more to a cambodian or cambodian more to a red. and pale bodied cambodians, marbles in any of those patterns.
The DTPK should improve the fins of the red PK. Theoretically you will have 100% DT geno - most single tails, some DT with uneven caudal lobes, single tails with longer dorsal. If you're lucky you might get more rays in the PK fry. Selectively breed F1 to get the ideal ray branching/form.
What are your plans/goals? What color is the marble DT? Is it a DTHM or a DTPK? By red, do you mean cherry red or extended red?
If your DT is not a red or not a cambodian, it would be a shame because you will ruin both colors. You see red is very difficult to clean out - like iridescence colors. So if your DT carry irid colors you will have non clean red fry (red with irids).