Regarding your question about the rear window large rubber and the gap. There are drains in the bottom of the panel that should be kept clean, Stevehose has a thread about the drains found here...https://e9coupe.com/forum/threads/check-your-rocker-panel-drain-holes.25566/ Don't use a hose to wash your car, I prefer a 3 gallon pressurized spray bottle to limit water usage and infiltration. The aluminum trim on the rocker cover is NLA to the best of my knowledge. May want to remove that strip and send them to a metal polishing company and have them straightened and either re anodized or ceramic coated. Regarding ceramic coating, there are several companies that have ceramic coat products. I have had 2 of my cars ceramic coated with Opti-Coat, my 2007 X3 & the 1988 M5. The coating is a cross link polymer chain that seals the paint and acts as a thin clear coat. In Maine the price tiers are $800, $1000 $1200 for the different levels of protection. I went with the $1200 on the X3 which came with all the Opti-coat products to maintain the finish and keep it clean and slippery. So far this winter I have been using a pressurized spray bottle to rinse off the salt every few days. Then the wash solution to wipe away surfactants then the Hyper Seal to keep it slippery. Ceramic coatings will help protect the paint from dust & dirt yet it will not protect from rock chips or other debris damage. Regarding Lokari fender liners, they are helpful to keep out debris, recommend removing them in the spring to clean out any salt or sand that finds its way around the rubber trim on the liner.