I don't really understand if you need to have all 5 criteria at once. So sorry if my recommendation is a bit off, since I can't think of one that with all those elements :^p
All I can come up with is Gaksital. There's romance, only most will agree that the female lead is a pretty bad actress -- still, the drama managed to be extremely popular in spite of that, so that must mean something!
(to be honest I'm not a fan of the show for various reasons, though I really understand its appeal and see why it's an interesting drama).
I think this drama contains points
- 2: he's a "robin hood" type of character, when Korea was occupied by the Japanese in the 40s, so there's a lot of fooling his ennemies going on (and he has a looooot of ennemies)
- 3: it's a very psychological drama, with a lot of growth on the lead's part
- sort of 4: he is an undercover hero after all, fighting for his country, but his second persona is far from clumsy, instead he acts cruel and collaborates with the Japanese