Assuming that Amazon & 1800 arch clearances aren't that dissimilar, then yes, that will be too much! On mine, running 15x7.5J (maybe 8J,not entirely sure which & no markings) Ansens & 205/65R15 tyres, even with pretty much identical backspace, and an additional 3" width outboard, the wheels are only just covered by the arches and the steering is a lot more sensitive to poor road surfaces. Your wheel choice looks like it will put the tyre centre of effort even further outboard of the steering axis...
Is there not any way that you can get thinner adaptors, or higher offset wheels?
Also, this link may be of use for working out and comparing wheel and tyre sizes, offsets & backspaces etc
http://www.rims-n-tires.com/rt_specs.jsp