That is a common place for it to tear, as the housing does not support it very well there. If you fumble at the install, it likes to tear there. If you back it up or remove it, it still likes to snag and tear there.
I have never used any sealants or glues, just the dry gasket.
I agree with Oldmanmopar that the weld is somewhat prone to leaking.
The last time I had the center section out of the 8.75 I reinstalled it with just a gasket, and it leaked, not much, a drip would form in an hour or so. Took it out, put a thin film of black rtv on both sides of the gasket and the leak was resolved.
Personally, I think that the cast iron, fully machined differential side is probably pretty good for flatness and sealing. It is the fabricated, welded together housing side that would be likely to have flatness and sealing issues.
