In the above game, I took 2 stones of handicap and lost by 9 points. I think I played well, though there are gaps in my playing and it shows in the transition from opening to middle game. I yet do not know how to attack in middle game and my opening moves might not be severe enough. For example, would
have been better off played as 
? I played as in the above game to maintain strategic consistency. Greed seems to be my main problem at the moment and I am trying to shake it off. Much obliged in advance for your input.
IMHO too much in the vicinity of already existing stones. The lower-left corner is somewhat settled for now, so this looks like trying to make territory with your influence in a very early phase. Instead I would try to claim additional influence in areas which are still more "undiscovered", most probably I would approach the top left corner at F17. Maybe some stronger player could give some even better advice. 
at K15: This looks somehow "disconnected". In the following, white could jump to O14 and O12 and then threaten to either surround your stone on a large scale or to invade right side.
at R5: This is really bad shape: The rule of thumb is: If you peep into a keima, you must cut in the next move. If cutting does not work (as in the game here), the peep is already mistaken. If 
just connects at S5, he is immediately alive (almost...). As an alternative you could have played the attach move R5 at 
, then 
on Q5 and 
- 
I'm not sure if playing out a broken ladder is much helpful. The w stones cannot be captured and it just hurts your E14 stones on left side. 
If w extends here at C13 it seems your black stones around there are just dead (as a consequence of the comment above). The Cosumi engine plays very generously here, but most human opponents wouldn't 