If you read the scenario header and manual, you will see where the de-orbit burn should take place when using p105, and it's not 180 degrees from the target. IIRC it's around 14.4M.
As stated in the DGIV manual, P105 isn't concerned with a target, it simply maintains a safe decent rate. Where you de-orbit will determine where you land, and your orbit's altitude determines how far ahead of the target you should de-orbit.
De-orbiting opposite the base makes for a long, gentle re-entry, and an AoA in the 30 to 35 degree range is needed to get the extra range required. The DGIV is designed to be de-orbited closer to the target, and the 40 degree AoA will bring you down quicker, but makes heat management more critical.