QuoteI picked the same ending for the same reasons. And yeah, the deserted planet crash is a big WTF. I'm not sure if you have to powergame the multiplayer to get the "best" ending. Did your end cutscene hint at Shepard's survival (by a person in N7 armour waking up in some rubble)?
Concerning the reaper's motives, I wouldn't object to leaving them unknown, or vague, as long as the ending wrapped up everything else nicely (including the reapers demise). Ramblings about chaos and order doesn't really explain anything though, as you mentioned.
But don't try to make sense of it. It only hurts. Just forget the whole ordeal and wait for BioWare to retcon this whole clusterfuck in a DLC.