I have a set of plastic ramps made by Davric Corporation that I've had for at least 10 years now and they haven't killed me yet
I don't recall what weight they're rated for but when I bought them I'm pretty sure that I made sure that the rating exceeded what I needed. Remember that none of these tools are going to be holding the entire weight of the vehicle. They're just holding one corner usually.
My floor jack that I use to tire work is rated for 3 tons, or 6000 lbs. I also have jack stands. Don't remember what they're rated for. Just use common sense and buy something that exceeds what you think a corner, or even half of the car weighs.
Can't tell you whether metric or American. Someone else here may be able to tell you, or worse case, get your ramps and raise the car up and see if your metric socket fits the oil plug.
My only other advice would be concerning the ramps. Years ago I had metal ramps which would probably give one more confidence than plastic ramps. My metal ramps though were very smooth which sometimes made a problem trying to get the car up on them. The front drive wheels would slip. Now if your AWD activates every time you start from a stop, then that would help because not all of the power is being applied to the front and the rears are pushing. Anyway, I don't even know if they still sell metal ramps (since everything is made out of plastic nowadays) but if they do, be aware that a smooth metal surface on the ramps could leave you slipping when trying to get up the incline. My plastic ramps have a surface that is not smooth.
That's all I can tell you for now. Good luck.