ARBs are easy, there is a How To on here somewhere, the creak will be the upper arm rather than the spring.
Rust is not a problem if it is away from the structural areas, eg holes by the seat belts anchor points, around the sill and subframe mounts etc etc. Looks like a good engine, if it had been losing oil those bits would be protected
TBH some looks like damage through an incorrectly placed trolley jack, the others by the sill need the underseal pulling off and rust removing to see what is going on.
The strut top looks normal, although the balljoint seal has clearly gone, but thats the part causing the creak (normally the other end of it), but there should be no play, as you say, probably the top mount, an easy fix seen as you are doing the upper arm.
In summary, any of those things on there own may have passed, but the whole lot does looks very dodgy IMO.