Just my opinion but I don't use brake cleaner to clean any places that I use gaskets and sealer. It seems to have a slight oily finish that needs to be cleaned off. I use an alcohol based cleaner and then dry that with a rag after I am sure that everything is clean. So far, and maybe just lucky, I have never had a gasket or seal leak. As for the
oil pan bolts I check mine every few times I drive it as they do tend to loosen once in a while. I would not use loctite on the bolts as you may want to take it off later. The best thing is just to spend a few minutes checking them every so often. After racing I used to spend a day going over my whole car checking all bolts with a torque wrench.
Ron