My betta is just great. He's really young. ;) I had Mango the guppy in the 5 gallon for a while as he (out of the blue) became uber-aggressive. I re-introduced him to my 10 gallon because my other guppy Hermes Jr has fin-rot . And now he's back in the 10 gallon too. ;D
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.