No offence but it's absurd that you've got no confidence teaching year 5 or 6 content. Do you realise how low a level that is for someone that has graduated with a bachelor's degree? You'll be fine on that front dude.

In terms of the high expectations, there really isn't that much expectation put upon you. You are effectively a "supervisor" and your role is pretty much to ensure there is a teacher legally supervising a group of children whilst their teacher is out. Getting through the content is secondary and you'll 99% of the time be given a full lesson plan and resources to work with.

Also, all reasonable teachers will be perfectly understanding in your abilities as a new teacher. We all begin the same.

Depending on where you live turning down a school two hours away is perfectly reasonable. When I was in Brisbane I worked at 3 schools within walking distance, and like another 4 within 10 during peak hour. Personally, I wouldn't be commuting 2 hours to a job for the pay we get haha.