I also did not go into my interview and say I'd do anything for the job.
I think that the OP didn't do that either.
If working in a remote site makes the OP uncomfortable there is nothing wrong with going to his bosses and saying that he in uncomfortable working with a female partner in the remote area. You have that right to ask that.
Unfortunately the bosses are going to come back and say that "this is the way the shifts fall" or "sorry, it's part of the job"
It sounds like the OP is doing the right thing by sleeping in a separate room.
There honestly should be separate sleeping quarters for women and men. The image of impropriety is always there and why continue to feed that image???
I have been in your shoes before, my wife and I enjoy good trust but when you are away from home for many hours and you are working with a partner of the opposite sex the other party simply cannot help but be concerned, even if there is nothing to be concerned about.
Continue to keep it completely platonic, sleep in separate rooms and keep your vows. If you are worried about your partner then you need to address that with your partner.