Your theory is way to complicated and would require the cooperation of too many things and people. I'm not biting. Sorry.
Let's talk about the current theory in those terms then:
[SIZE=+1]WHAT MIGHT HAVE GONE WRONG IF CHRIS WAS THE KILLER:[/SIZE]
-Erin gets major morning sickness(I love HIMYM), not up for celebrating
-Jon finds period tracker early, big fight, Erin can't go
-Nichole sick, can't take care of daughter, Chris can't go
-Lore surprises Erin with early visit, Erin can't go
-Food poisoning, comrade's bad tacos mean Chris called for duty
-TN friend tells Jon about continuing affair, big fight, Erin can't go
-Drunk marine buddy pulls prank. Pees in Jeep gas tank. Chris def can't go
-Bad paperwork, no ammo, training cancelled and Jon wants to go with Erin to JT
-Big thunderstorms, fake hunting trip story out the window, Erin won't go
-Chris hung over from party, can't make it today, too sick.
-When Chris asks guys to go hunting with him, they actually accept this time.
-Wildfire spreads south of JT, Rangers close park for smoke, Erin's alibi caput.
-Chris' 17 year old, heavily used vehicle breaks down at some point during the day.
-Improperly cleaned gun jams, Erin kicks him in the nuts and runs away.
-Erin freaks out because they're not going where he said they were going. (suspicious, or too hot, etc.)
-Erin plans her own surprise for their outing, won't go hunting.
-Low flying plane sees Chris and Erin and Jeep where they shouldn't be. Chris calls it off.
-Chris stumbles carrying unconscious Erin up steep incline on way to mine, breaks leg, must call 911
-Lost gold seekers come across Chris where he shouldn't be, Chris arrested.
Feel Free To Add More Of Your Own.
As you can see, all plans require lots of cooperation. Some plans succeed despite the odds. Unfortunately, someone's plan worked, and who's it was remains to be seen.