OK, first thing to note here is the advice about NEVER towing the 4x4 with the front wheels off the ground. Must always be towed with all 4 wheels turning, or the viscous diff will blow itself apart almost instantly. Same is true for trying to do handbrake turns in the snow - don't do it!
Anyway, P1121 is;
P1121 Pedal Position 1 Range/Performance Problem
This suggests your 4x4 is like mine and has a Fly-by-Wire throttle body, in that there's no mechanical link between pedal and butterfly. Although the symptoms have now passed, if they do happen again you need to check the operation of the butterfly visually. Simply remove the airbox (a couple of 10mm bolts) and pull the entire airbox clear of the throttle-body (TB). In the mouth of the TB you'll see the smallest of butterfly valves (no wonder the engines feel a bit restricted beyond 5k...!) and this should open full range when the engine is rev'd. In fact I recall it goes through a full range deflection test when ignition is switched on too - either way, look at the behaviour now, whilst the engine runs fine and then again when it goes wrong. That way you'll know for sure.
P1015 makes reference to Fuel Circuit, which may just be an associated failure message. However, also check the connection to the TB - there's a yellow/black multiblock connector to the right of the TB and this needs to be clean and properly fitted. Worth a check and clean up regardless.
Let us know how you get on.
PG