Ipd sells new wiper blades.
The rear license plate swivels so that you can read (or the police can read) the license plate with the tailgate down. Apparently the Swedes weren't too worried about CO issues back then. Now there are all sorts of warnings in wagon owner's manuals about this. Complete exploded diagram and support parts are available at vintageimportparts.com, among other providers.
Oil drain nut was originally 1".
I use 15w-40 synthetic (Amsoil) in my 220, and it seems to run fine.
Your oil pressure sounds great! Congratulations.
Yes, any red block oil filter, and I think most of the white block filters are great and also fit. Just be sure to use one with the anti-drain back valve, which the Mann's (OE)) have.
You can raise the car on a pair of jackstands under the axle and rotate the adjuster out a little bit and see if the tire gets harder to turn. A manual will go in to this in more depth. You will need to buy, borrow or make a drum puller ($100.00) to service the rear brakes on this car. Treat your brake drums very well, as they are quite expensive to replace.
The rheostat for the lights is available, but I don't think I would worry about getting a new one at this time..if the switch works, stick with it. All of the window rubber is available new, as is the doors.($$$). For now, some sealing caulk will help slow down the rain.
The drain for the heater box is a chronic issue on these cars. You can pop the grille out easily and take a vacuum cleaner down in there, but this is not as good or as complete as disassembling the box, and clean out the whole shooting match, repaint and re-gasket it , and re-assemble. A good week-end project. Good luck, these are fun little cars.
Gap spec should be in a Haynes manual. IIRC .018? Don't quote me on this one.