Amazon, Aircraft Spruce, and Ebay are your friends in finding unusual lubricants. I don't remember any particular difficulties finding the Lycoming specified ones when I did my engine.
On the case, I used locktite without the silk thread, which has worked fine. I can't tell you if the other choices are better or worse. At that point, it is probably down to the skill or attention to detail of the assembler and the condition of the case halves rather than the specific sealant used.
2001 RV-6 N46KB