It might be worth investing in some good cavity wax and squirting it into as many seams and crevices as you can, to keep things ok until you want to do anything more major. Various opinions on here as to what's best but I like Bilt Hamber Dynax S50.
The car will now live in Los Angeles, parked indoors, with weekend use split between it and my 911. It won't see very much (if any rain), so the rust should hopefully not progress.
Fair enough! Though prevention is better than cure...
I agree, I'd also recommend that the rust (and the car checked for any hidden repairs) is dealt with ASAP so it doesn't get worse.
As for the knock ypu ideally need to get a pry bar to check for split mounts or snapped mounts