I couldn't tell you if the sensors would work. They might just temporarily mask an underlying problem. Have you dropped the oil pan?
I should redo my last post...I'll do that here:
As for the hard cranking, I don't think that's anything to do with the transmission unless you have a something major going on like the torque convertor or oil pump piled up inside? Probably unrelated but maybe your battery cables are badly corroded or weak battery causing problems?
It acts like it's stuck in B mode and revs too high. Are you positive the fluid level is correct? I don't think I ran into one acting like that but the car in the one link I posted did throw that same P0791 code then eventually acted like it was slipping so I just replaced the entire unit.
$300 would go a long ways towards a used cvt.
Have you ever replaced any of the filters in the cvt, mainly the one on the side of the case? I had a comment on one of my vijeo's form someone that worked at Mitsu(not sure if dealer or ?) and said that Mitsubishi got irritated with the number of warranty cvt's that were replaced that just had the cartridge filter plugged and had no other damage. I don't know if that's true or if they had no visible damage but the valve body was hooped like the case was in my own cvt that I tore down
here.
I'd hate to see you throw $300 at it and it not fix the problem.