1. Stopping that lens down to f/11 is perfectly ok. F/8 and F/16 are fine too. There's usually no problem with diffraction when going down 2 or 3 stops from wide open. Softness due to diffraction is dependent upon the actual size of the iris opening, not the f stop which is nothing more than a ratio: focal length / aperture size. A lens with a focal length of 80 mm. will have a smaller f number than a shorter lens given the same sized opening. That's why you can stop long lenses down a lot more before diffraction problems begin to show up. As far as the aperture used affecting the contrast, no that's not a problem. I'm guessing that it might be if your exposure times are so long that reciprocity failure sets in, but I've never seen that happen with exposure times up to 2 minutes. Most of my exposures run from around 10 to 45 seconds, so I haven't really though about testing for the problem.

2. Red safelights are fine. They may even be more safe than the standard OC spec safelights usually recommended by the paper manufacturer. The reason many manufacturers recommend the OC spec safelights is that it is much easier for humans to see under those conditions, while still being safe for their variable contrast papers. I'm using 3 Kodak beehive type safelights equipped with red 1A filters and 15 watt incandescent lamps with all kinds of papers and orthochromatic films and they are safe. The distance from your workspace is good. The minimum recommended distance is usually specified at about 4 ft or 1.4 meters. You're good there. The only reason to switch over to the OC spec. safelights is if you're having problems seeing under red light.

3. AN glass is always good to have if you're using a glass type negative carrier, but not always completely necessary. A lot depends upon they type of film and the weather conditions. Films that have a very smooth and almost shiny emulsion side (think Kodak's TMax films) benefit the most. I use glassless carriers myself. I don't see much, if any difference in sharpness for the print sizes I make, and it's 4 fewer surfaces to keep dust free.

4. Touch up paint to use where? Rustoleum is good for just about any metal surface.

5. Resin coated papers, Ilford's or any others for that matter, because the support does not absorb any water, develop, fix, and wash out far more quickly than fiber based papers. Only the solutions that have absorbed into the very thin gelatine emulsion need to be removed. Two to four minutes in the wash is usually sufficient. If your tap water is very cold, it can take a little longer.Water penetrating the edges can be a problem if you overdo the wet time, but you relly need to overdo it by a lot. I've left prints sitting in a tub of water for an hour with no apparent damage. At worst, if you see a tiny bit of de-lamination at the corners of the print, it's a simple matter to trim the edges down a little bit to remove it. You are leaving a border, right?