I use a rubber mallet and tap on the bottom bolts once I have all the top bolts and bottom nuts removed. This is safer than prying on the gasket surfaces and won't damage the threads. Also, did you remove your timing plate?
Yes, you can reweld or rebraze the little piece back on. I did that recently with a mapp gas torch and some aluminum brazing rod. Make sure you file the case and the broken part to form a small "v" when you hold them back together. This will give the rod a better bonding surface.
Also, if you have a billet stator cover, you can bolt that in place (without the gasket) to hold the broken piece in place while you braze or weld it back on.